clojure.core
Fundamental library of the Clojure language
*1
bound in a repl thread to the most recent value printed
*2
bound in a repl thread to the second most recent value printed
*3
bound in a repl thread to the third most recent value printed
*agent*
The agent currently running an action on this thread, else nil
*clojure-version*
The version info for Clojure core, as a map containing :major :minor
:incremental and :qualifier keys. Feature releases may increment
:minor and/or :major, bugfix releases will increment :incremental.
Possible values of :qualifier include "GA", "SNAPSHOT", "RC-x" "BETA-x"
*command-line-args*
A sequence of the supplied command line arguments, or nil if
none were supplied
*compile-path*
Specifies the directory where 'compile' will write out .class
files. This directory must be in the classpath for 'compile' to
work.
Defaults to "classes"
*compiler-options*
A map of keys to options.
Note, when binding dynamically make sure to merge with previous value.
Supported options:
:elide-meta - a collection of metadata keys to elide during compilation.
:disable-locals-clearing - set to true to disable clearing, useful for using a debugger
Alpha, subject to change.
*data-readers*
Map from reader tag symbols to data reader Vars.
When Clojure starts, it searches for files named 'data_readers.clj'
and 'data_readers.cljc' at the root of the classpath. Each such file
must contain a literal map of symbols, like this:
{foo/bar my.project.foo/bar
foo/baz my.project/baz}
The first symbol in each pair is a tag that will be recognized by
the Clojure reader. The second symbol in the pair is the
fully-qualified name of a Var which will be invoked by the reader to
parse the form following the tag. For example, given the
data_readers.clj file above, the Clojure reader would parse this
form:
#foo/bar [1 2 3]
by invoking the Var #'my.project.foo/bar on the vector [1 2 3]. The
data reader function is invoked on the form AFTER it has been read
as a normal Clojure data structure by the reader.
Reader tags without namespace qualifiers are reserved for
Clojure. Default reader tags are defined in
clojure.core/default-data-readers but may be overridden in
data_readers.clj, data_readers.cljc, or by rebinding this Var.
*default-data-reader-fn*
When no data reader is found for a tag and *default-data-reader-fn*
is non-nil, it will be called with two arguments,
the tag and the value. If *default-data-reader-fn* is nil (the
default), an exception will be thrown for the unknown tag.
*e
bound in a repl thread to the most recent exception caught by the repl
*err*
A java.io.Writer object representing standard error for print operations.
Defaults to System/err, wrapped in a PrintWriter
*file*
The path of the file being evaluated, as a String.
When there is no file, e.g. in the REPL, the value is not defined.
*flush-on-newline*
When set to true, output will be flushed whenever a newline is printed.
Defaults to true.
*in*
A java.io.Reader object representing standard input for read operations.
Defaults to System/in, wrapped in a LineNumberingPushbackReader
*ns*
A clojure.lang.Namespace object representing the current namespace.
*out*
A java.io.Writer object representing standard output for print operations.
Defaults to System/out, wrapped in an OutputStreamWriter
*print-dup*
When set to logical true, objects will be printed in a way that preserves
their type when read in later.
Defaults to false.
*print-length*
*print-length* controls how many items of each collection the
printer will print. If it is bound to logical false, there is no
limit. Otherwise, it must be bound to an integer indicating the maximum
number of items of each collection to print. If a collection contains
more items, the printer will print items up to the limit followed by
'...' to represent the remaining items. The root binding is nil
indicating no limit.
*print-level*
*print-level* controls how many levels deep the printer will
print nested objects. If it is bound to logical false, there is no
limit. Otherwise, it must be bound to an integer indicating the maximum
level to print. Each argument to print is at level 0; if an argument is a
collection, its items are at level 1; and so on. If an object is a
collection and is at a level greater than or equal to the value bound to
*print-level*, the printer prints '#' to represent it. The root binding
is nil indicating no limit.
*print-meta*
If set to logical true, when printing an object, its metadata will also
be printed in a form that can be read back by the reader.
Defaults to false.
*print-namespace-maps*
*print-namespace-maps* controls whether the printer will print
namespace map literal syntax. It defaults to false, but the REPL binds
to true.
*print-readably*
When set to logical false, strings and characters will be printed with
non-alphanumeric characters converted to the appropriate escape sequences.
Defaults to true
*read-eval*
Defaults to true (or value specified by system property, see below)
***This setting implies that the full power of the reader is in play,
including syntax that can cause code to execute. It should never be
used with untrusted sources. See also: clojure.edn/read.***
When set to logical false in the thread-local binding,
the eval reader (#=) and record/type literal syntax are disabled in read/load.
Example (will fail): (binding [*read-eval* false] (read-string "#=(* 2 21)"))
The default binding can be controlled by the system property
'clojure.read.eval' System properties can be set on the command line
like this:
java -Dclojure.read.eval=false ...
The system property can also be set to 'unknown' via
-Dclojure.read.eval=unknown, in which case the default binding
is :unknown and all reads will fail in contexts where *read-eval*
has not been explicitly bound to either true or false. This setting
can be a useful diagnostic tool to ensure that all of your reads
occur in considered contexts. You can also accomplish this in a
particular scope by binding *read-eval* to :unknown
*unchecked-math*
While bound to true, compilations of +, -, *, inc, dec and the
coercions will be done without overflow checks. While bound
to :warn-on-boxed, same behavior as true, and a warning is emitted
when compilation uses boxed math. Default: false.
*warn-on-reflection*
When set to true, the compiler will emit warnings when reflection is
needed to resolve Java method calls or field accesses.
Defaults to false.
(- x)
(- x y)
(- x y & more)
If no ys are supplied, returns the negation of x, else subtracts
the ys from x and returns the result. Does not auto-promote
longs, will throw on overflow. See also: -'
(-' x)
(-' x y)
(-' x y & more)
If no ys are supplied, returns the negation of x, else subtracts
the ys from x and returns the result. Supports arbitrary precision.
See also: -
(-> x & forms)
Threads the expr through the forms. Inserts x as the
second item in the first form, making a list of it if it is not a
list already. If there are more forms, inserts the first form as the
second item in second form, etc.
(->> x & forms)
Threads the expr through the forms. Inserts x as the
last item in the first form, making a list of it if it is not a
list already. If there are more forms, inserts the first form as the
last item in second form, etc.
(.. x form)
(.. x form & more)
form => fieldName-symbol or (instanceMethodName-symbol args*)
Expands into a member access (.) of the first member on the first
argument, followed by the next member on the result, etc. For
instance:
(.. System (getProperties) (get "os.name"))
expands to:
(. (. System (getProperties)) (get "os.name"))
but is easier to write, read, and understand.
(/ x)
(/ x y)
(/ x y & more)
If no denominators are supplied, returns 1/numerator,
else returns numerator divided by all of the denominators.
(= x)
(= x y)
(= x y & more)
Equality. Returns true if x equals y, false if not. Same as
Java x.equals(y) except it also works for nil, and compares
numbers and collections in a type-independent manner. Clojure's immutable data
structures define equals() (and thus =) as a value, not an identity,
comparison.
(accessor s key)
Returns a fn that, given an instance of a structmap with the basis,
returns the value at the key. The key must be in the basis. The
returned function should be (slightly) more efficient than using
get, but such use of accessors should be limited to known
performance-critical areas.
(aclone array)
Returns a clone of the Java array. Works on arrays of known
types.
(add-classpath url)
DEPRECATED
Adds the url (String or URL object) to the classpath per
URLClassLoader.addURL
(add-watch reference key fn)
Adds a watch function to an agent/atom/var/ref reference. The watch
fn must be a fn of 4 args: a key, the reference, its old-state, its
new-state. Whenever the reference's state might have been changed,
any registered watches will have their functions called. The watch fn
will be called synchronously, on the agent's thread if an agent,
before any pending sends if agent or ref. Note that an atom's or
ref's state may have changed again prior to the fn call, so use
old/new-state rather than derefing the reference. Note also that watch
fns may be called from multiple threads simultaneously. Var watchers
are triggered only by root binding changes, not thread-local
set!s. Keys must be unique per reference, and can be used to remove
the watch with remove-watch, but are otherwise considered opaque by
the watch mechanism.
(agent state & options)
Creates and returns an agent with an initial value of state and
zero or more options (in any order):
:meta metadata-map
:validator validate-fn
:error-handler handler-fn
:error-mode mode-keyword
If metadata-map is supplied, it will become the metadata on the
agent. validate-fn must be nil or a side-effect-free fn of one
argument, which will be passed the intended new state on any state
change. If the new state is unacceptable, the validate-fn should
return false or throw an exception. handler-fn is called if an
action throws an exception or if validate-fn rejects a new state --
see set-error-handler! for details. The mode-keyword may be either
:continue (the default if an error-handler is given) or :fail (the
default if no error-handler is given) -- see set-error-mode! for
details.
(agent-error a)
Returns the exception thrown during an asynchronous action of the
agent if the agent is failed. Returns nil if the agent is not
failed.
(agent-errors a)
DEPRECATED: Use 'agent-error' instead.
Returns a sequence of the exceptions thrown during asynchronous
actions of the agent.
(alength array)
Returns the length of the Java array. Works on arrays of all
types.
(alias alias namespace-sym)
Add an alias in the current namespace to another
namespace. Arguments are two symbols: the alias to be used, and
the symbolic name of the target namespace. Use :as in the ns macro in preference
to calling this directly.
(all-ns)
Returns a sequence of all namespaces.
(alter ref fun & args)
Must be called in a transaction. Sets the in-transaction-value of
ref to:
(apply fun in-transaction-value-of-ref args)
and returns the in-transaction-value of ref.
(alter-meta! iref f & args)
Atomically sets the metadata for a namespace/var/ref/agent/atom to be:
(apply f its-current-meta args)
f must be free of side-effects
(amap a idx ret expr)
Maps an expression across an array a, using an index named idx, and
return value named ret, initialized to a clone of a, then setting
each element of ret to the evaluation of expr, returning the new
array ret.
(ancestors tag)
(ancestors h tag)
Returns the immediate and indirect parents of tag, either via a Java type
inheritance relationship or a relationship established via derive. h
must be a hierarchy obtained from make-hierarchy, if not supplied
defaults to the global hierarchy
(and)
(and x)
(and x & next)
Evaluates exprs one at a time, from left to right. If a form
returns logical false (nil or false), and returns that value and
doesn't evaluate any of the other expressions, otherwise it returns
the value of the last expr. (and) returns true.
(any? x)
Returns true given any argument.
(areduce a idx ret init expr)
Reduces an expression across an array a, using an index named idx,
and return value named ret, initialized to init, setting ret to the
evaluation of expr at each step, returning ret.
(as-> expr name & forms)
Binds name to expr, evaluates the first form in the lexical context
of that binding, then binds name to that result, repeating for each
successive form, returning the result of the last form.
(assoc map key val)
(assoc map key val & kvs)
assoc[iate]. When applied to a map, returns a new map of the
same (hashed/sorted) type, that contains the mapping of key(s) to
val(s). When applied to a vector, returns a new vector that
contains val at index. Note - index must be <= (count vector).
(assoc-in m [k & ks] v)
Associates a value in a nested associative structure, where ks is a
sequence of keys and v is the new value and returns a new nested structure.
If any levels do not exist, hash-maps will be created.
(atom x)
(atom x & options)
Creates and returns an Atom with an initial value of x and zero or
more options (in any order):
:meta metadata-map
:validator validate-fn
If metadata-map is supplied, it will become the metadata on the
atom. validate-fn must be nil or a side-effect-free fn of one
argument, which will be passed the intended new state on any state
change. If the new state is unacceptable, the validate-fn should
return false or throw an exception.
(await & agents)
Blocks the current thread (indefinitely!) until all actions
dispatched thus far, from this thread or agent, to the agent(s) have
occurred. Will block on failed agents. Will never return if
a failed agent is restarted with :clear-actions true or shutdown-agents was called.
(await-for timeout-ms & agents)
Blocks the current thread until all actions dispatched thus
far (from this thread or agent) to the agents have occurred, or the
timeout (in milliseconds) has elapsed. Returns logical false if
returning due to timeout, logical true otherwise.
(bases c)
Returns the immediate superclass and direct interfaces of c, if any
(bean x)
Takes a Java object and returns a read-only implementation of the
map abstraction based upon its JavaBean properties.
(binding bindings & body)
binding => var-symbol init-expr
Creates new bindings for the (already-existing) vars, with the
supplied initial values, executes the exprs in an implicit do, then
re-establishes the bindings that existed before. The new bindings
are made in parallel (unlike let); all init-exprs are evaluated
before the vars are bound to their new values.
(bound-fn & fntail)
Returns a function defined by the given fntail, which will install the
same bindings in effect as in the thread at the time bound-fn was called.
This may be used to define a helper function which runs on a different
thread, but needs the same bindings in place.
(bound-fn* f)
Returns a function, which will install the same bindings in effect as in
the thread at the time bound-fn* was called and then call f with any given
arguments. This may be used to define a helper function which runs on a
different thread, but needs the same bindings in place.
(bound? & vars)
Returns true if all of the vars provided as arguments have any bound value, root or thread-local.
Implies that deref'ing the provided vars will succeed. Returns true if no vars are provided.
(bounded-count n coll)
If coll is counted? returns its count, else will count at most the first n
elements of coll using its seq
(butlast coll)
Return a seq of all but the last item in coll, in linear time
(case e & clauses)
Takes an expression, and a set of clauses.
Each clause can take the form of either:
test-constant result-expr
(test-constant1 ... test-constantN) result-expr
The test-constants are not evaluated. They must be compile-time
literals, and need not be quoted. If the expression is equal to a
test-constant, the corresponding result-expr is returned. A single
default expression can follow the clauses, and its value will be
returned if no clause matches. If no default expression is provided
and no clause matches, an IllegalArgumentException is thrown.
Unlike cond and condp, case does a constant-time dispatch, the
clauses are not considered sequentially. All manner of constant
expressions are acceptable in case, including numbers, strings,
symbols, keywords, and (Clojure) composites thereof. Note that since
lists are used to group multiple constants that map to the same
expression, a vector can be used to match a list if needed. The
test-constants need not be all of the same type.
(cast c x)
Throws a ClassCastException if x is not a c, else returns x.
(cat rf)
A transducer which concatenates the contents of each input, which must be a
collection, into the reduction.
(class? x)
Returns true if x is an instance of Class
(clear-agent-errors a)
DEPRECATED: Use 'restart-agent' instead.
Clears any exceptions thrown during asynchronous actions of the
agent, allowing subsequent actions to occur.
(coll? x)
Returns true if x implements IPersistentCollection
(commute ref fun & args)
Must be called in a transaction. Sets the in-transaction-value of
ref to:
(apply fun in-transaction-value-of-ref args)
and returns the in-transaction-value of ref.
At the commit point of the transaction, sets the value of ref to be:
(apply fun most-recently-committed-value-of-ref args)
Thus fun should be commutative, or, failing that, you must accept
last-one-in-wins behavior. commute allows for more concurrency than
ref-set.
(comp)
(comp f)
(comp f g)
(comp f g & fs)
Takes a set of functions and returns a fn that is the composition
of those fns. The returned fn takes a variable number of args,
applies the rightmost of fns to the args, the next
fn (right-to-left) to the result, etc.
(compare x y)
Comparator. Returns a negative number, zero, or a positive number
when x is logically 'less than', 'equal to', or 'greater than'
y. Same as Java x.compareTo(y) except it also works for nil, and
compares numbers and collections in a type-independent manner. x
must implement Comparable
(compare-and-set! atom oldval newval)
Atomically sets the value of atom to newval if and only if the
current value of the atom is identical to oldval. Returns true if
set happened, else false
(compile lib)
Compiles the namespace named by the symbol lib into a set of
classfiles. The source for the lib must be in a proper
classpath-relative directory. The output files will go into the
directory specified by *compile-path*, and that directory too must
be in the classpath.
(complement f)
Takes a fn f and returns a fn that takes the same arguments as f,
has the same effects, if any, and returns the opposite truth value.
(completing f)
(completing f cf)
Takes a reducing function f of 2 args and returns a fn suitable for
transduce by adding an arity-1 signature that calls cf (default -
identity) on the result argument.
(cond & clauses)
Takes a set of test/expr pairs. It evaluates each test one at a
time. If a test returns logical true, cond evaluates and returns
the value of the corresponding expr and doesn't evaluate any of the
other tests or exprs. (cond) returns nil.
(cond-> expr & clauses)
Takes an expression and a set of test/form pairs. Threads expr (via ->)
through each form for which the corresponding test
expression is true. Note that, unlike cond branching, cond-> threading does
not short circuit after the first true test expression.
(cond->> expr & clauses)
Takes an expression and a set of test/form pairs. Threads expr (via ->>)
through each form for which the corresponding test expression
is true. Note that, unlike cond branching, cond->> threading does not short circuit
after the first true test expression.
(condp pred expr & clauses)
Takes a binary predicate, an expression, and a set of clauses.
Each clause can take the form of either:
test-expr result-expr
test-expr :>> result-fn
Note :>> is an ordinary keyword.
For each clause, (pred test-expr expr) is evaluated. If it returns
logical true, the clause is a match. If a binary clause matches, the
result-expr is returned, if a ternary clause matches, its result-fn,
which must be a unary function, is called with the result of the
predicate as its argument, the result of that call being the return
value of condp. A single default expression can follow the clauses,
and its value will be returned if no clause matches. If no default
expression is provided and no clause matches, an
IllegalArgumentException is thrown.
(conj coll x)
(conj coll x & xs)
conj[oin]. Returns a new collection with the xs
'added'. (conj nil item) returns (item). The 'addition' may
happen at different 'places' depending on the concrete type.
(conj!)
(conj! coll)
(conj! coll x)
Adds x to the transient collection, and return coll. The 'addition'
may happen at different 'places' depending on the concrete type.
(cons x seq)
Returns a new seq where x is the first element and seq is
the rest.
(constantly x)
Returns a function that takes any number of arguments and returns x.
(contains? coll key)
Returns true if key is present in the given collection, otherwise
returns false. Note that for numerically indexed collections like
vectors and Java arrays, this tests if the numeric key is within the
range of indexes. 'contains?' operates constant or logarithmic time;
it will not perform a linear search for a value. See also 'some'.
(count coll)
Returns the number of items in the collection. (count nil) returns
0. Also works on strings, arrays, and Java Collections and Maps
(create-ns sym)
Create a new namespace named by the symbol if one doesn't already
exist, returns it or the already-existing namespace of the same
name.
(cycle coll)
Returns a lazy (infinite!) sequence of repetitions of the items in coll.
(dec x)
Returns a number one less than num. Does not auto-promote
longs, will throw on overflow. See also: dec'
(dec' x)
Returns a number one less than num. Supports arbitrary precision.
See also: dec
(declare & names)
defs the supplied var names with no bindings, useful for making forward declarations.
(dedupe)
(dedupe coll)
Returns a lazy sequence removing consecutive duplicates in coll.
Returns a transducer when no collection is provided.
default-data-readers
Default map of data reader functions provided by Clojure. May be
overridden by binding *data-readers*.
(definline name & decl)
Experimental - like defmacro, except defines a named function whose
body is the expansion, calls to which may be expanded inline as if
it were a macro. Cannot be used with variadic (&) args.
(definterface name & sigs)
Creates a new Java interface with the given name and method sigs.
The method return types and parameter types may be specified with type hints,
defaulting to Object if omitted.
(definterface MyInterface
(^int method1 [x])
(^Bar method2 [^Baz b ^Quux q]))
(defmulti name docstring? attr-map? dispatch-fn & options)
Creates a new multimethod with the associated dispatch function.
The docstring and attr-map are optional.
Options are key-value pairs and may be one of:
:default
The default dispatch value, defaults to :default
:hierarchy
The value used for hierarchical dispatch (e.g. ::square is-a ::shape)
Hierarchies are type-like relationships that do not depend upon type
inheritance. By default Clojure's multimethods dispatch off of a
global hierarchy map. However, a hierarchy relationship can be
created with the derive function used to augment the root ancestor
created with make-hierarchy.
Multimethods expect the value of the hierarchy option to be supplied as
a reference type e.g. a var (i.e. via the Var-quote dispatch macro #'
or the var special form).
(defonce name expr)
defs name to have the root value of the expr iff the named var has no root value,
else expr is unevaluated
(defprotocol name & opts+sigs)
A protocol is a named set of named methods and their signatures:
(defprotocol AProtocolName
;optional doc string
"A doc string for AProtocol abstraction"
;method signatures
(bar [this a b] "bar docs")
(baz [this a] [this a b] [this a b c] "baz docs"))
No implementations are provided. Docs can be specified for the
protocol overall and for each method. The above yields a set of
polymorphic functions and a protocol object. All are
namespace-qualified by the ns enclosing the definition The resulting
functions dispatch on the type of their first argument, which is
required and corresponds to the implicit target object ('this' in
Java parlance). defprotocol is dynamic, has no special compile-time
effect, and defines no new types or classes. Implementations of
the protocol methods can be provided using extend.
defprotocol will automatically generate a corresponding interface,
with the same name as the protocol, i.e. given a protocol:
my.ns/Protocol, an interface: my.ns.Protocol. The interface will
have methods corresponding to the protocol functions, and the
protocol will automatically work with instances of the interface.
Note that you should not use this interface with deftype or
reify, as they support the protocol directly:
(defprotocol P
(foo [this])
(bar-me [this] [this y]))
(deftype Foo [a b c]
P
(foo [this] a)
(bar-me [this] b)
(bar-me [this y] (+ c y)))
(bar-me (Foo. 1 2 3) 42)
=> 45
(foo
(let [x 42]
(reify P
(foo [this] 17)
(bar-me [this] x)
(bar-me [this y] x))))
=> 17
(defrecord name [& fields] & opts+specs)
(defrecord name [fields*] options* specs*)
Options are expressed as sequential keywords and arguments (in any order).
Supported options:
:load-ns - if true, importing the record class will cause the
namespace in which the record was defined to be loaded.
Defaults to false.
Each spec consists of a protocol or interface name followed by zero
or more method bodies:
protocol-or-interface-or-Object
(methodName [args*] body)*
Dynamically generates compiled bytecode for class with the given
name, in a package with the same name as the current namespace, the
given fields, and, optionally, methods for protocols and/or
interfaces.
The class will have the (immutable) fields named by
fields, which can have type hints. Protocols/interfaces and methods
are optional. The only methods that can be supplied are those
declared in the protocols/interfaces. Note that method bodies are
not closures, the local environment includes only the named fields,
and those fields can be accessed directly.
Method definitions take the form:
(methodname [args*] body)
The argument and return types can be hinted on the arg and
methodname symbols. If not supplied, they will be inferred, so type
hints should be reserved for disambiguation.
Methods should be supplied for all methods of the desired
protocol(s) and interface(s). You can also define overrides for
methods of Object. Note that a parameter must be supplied to
correspond to the target object ('this' in Java parlance). Thus
methods for interfaces will take one more argument than do the
interface declarations. Note also that recur calls to the method
head should *not* pass the target object, it will be supplied
automatically and can not be substituted.
In the method bodies, the (unqualified) name can be used to name the
class (for calls to new, instance? etc).
The class will have implementations of several (clojure.lang)
interfaces generated automatically: IObj (metadata support) and
IPersistentMap, and all of their superinterfaces.
In addition, defrecord will define type-and-value-based =,
and will defined Java .hashCode and .equals consistent with the
contract for java.util.Map.
When AOT compiling, generates compiled bytecode for a class with the
given name (a symbol), prepends the current ns as the package, and
writes the .class file to the *compile-path* directory.
Two constructors will be defined, one taking the designated fields
followed by a metadata map (nil for none) and an extension field
map (nil for none), and one taking only the fields (using nil for
meta and extension fields). Note that the field names __meta,
__extmap, __hash and __hasheq are currently reserved and should not
be used when defining your own records.
Given (defrecord TypeName ...), two factory functions will be
defined: ->TypeName, taking positional parameters for the fields,
and map->TypeName, taking a map of keywords to field values.
(deftype name [& fields] & opts+specs)
(deftype name [fields*] options* specs*)
Options are expressed as sequential keywords and arguments (in any order).
Supported options:
:load-ns - if true, importing the type class will cause the
namespace in which the type was defined to be loaded.
Defaults to false.
Each spec consists of a protocol or interface name followed by zero
or more method bodies:
protocol-or-interface-or-Object
(methodName [args*] body)*
Dynamically generates compiled bytecode for class with the given
name, in a package with the same name as the current namespace, the
given fields, and, optionally, methods for protocols and/or
interfaces.
The class will have the (by default, immutable) fields named by
fields, which can have type hints. Protocols/interfaces and methods
are optional. The only methods that can be supplied are those
declared in the protocols/interfaces. Note that method bodies are
not closures, the local environment includes only the named fields,
and those fields can be accessed directly. Fields can be qualified
with the metadata :volatile-mutable true or :unsynchronized-mutable
true, at which point (set! afield aval) will be supported in method
bodies. Note well that mutable fields are extremely difficult to use
correctly, and are present only to facilitate the building of higher
level constructs, such as Clojure's reference types, in Clojure
itself. They are for experts only - if the semantics and
implications of :volatile-mutable or :unsynchronized-mutable are not
immediately apparent to you, you should not be using them.
Method definitions take the form:
(methodname [args*] body)
The argument and return types can be hinted on the arg and
methodname symbols. If not supplied, they will be inferred, so type
hints should be reserved for disambiguation.
Methods should be supplied for all methods of the desired
protocol(s) and interface(s). You can also define overrides for
methods of Object. Note that a parameter must be supplied to
correspond to the target object ('this' in Java parlance). Thus
methods for interfaces will take one more argument than do the
interface declarations. Note also that recur calls to the method
head should *not* pass the target object, it will be supplied
automatically and can not be substituted.
In the method bodies, the (unqualified) name can be used to name the
class (for calls to new, instance? etc).
When AOT compiling, generates compiled bytecode for a class with the
given name (a symbol), prepends the current ns as the package, and
writes the .class file to the *compile-path* directory.
One constructor will be defined, taking the designated fields. Note
that the field names __meta, __extmap, __hash and __hasheq are currently
reserved and should not be used when defining your own types.
Given (deftype TypeName ...), a factory function called ->TypeName
will be defined, taking positional parameters for the fields
(delay & body)
Takes a body of expressions and yields a Delay object that will
invoke the body only the first time it is forced (with force or deref/@), and
will cache the result and return it on all subsequent force
calls. See also - realized?
(delay? x)
returns true if x is a Delay created with delay
(deliver promise val)
Delivers the supplied value to the promise, releasing any pending
derefs. A subsequent call to deliver on a promise will have no effect.
(deref ref)
(deref ref timeout-ms timeout-val)
Also reader macro: @ref/@agent/@var/@atom/@delay/@future/@promise. Within a transaction,
returns the in-transaction-value of ref, else returns the
most-recently-committed value of ref. When applied to a var, agent
or atom, returns its current state. When applied to a delay, forces
it if not already forced. When applied to a future, will block if
computation not complete. When applied to a promise, will block
until a value is delivered. The variant taking a timeout can be
used for blocking references (futures and promises), and will return
timeout-val if the timeout (in milliseconds) is reached before a
value is available. See also - realized?.
(derive tag parent)
(derive h tag parent)
Establishes a parent/child relationship between parent and
tag. Parent must be a namespace-qualified symbol or keyword and
child can be either a namespace-qualified symbol or keyword or a
class. h must be a hierarchy obtained from make-hierarchy, if not
supplied defaults to, and modifies, the global hierarchy.
(descendants tag)
(descendants h tag)
Returns the immediate and indirect children of tag, through a
relationship established via derive. h must be a hierarchy obtained
from make-hierarchy, if not supplied defaults to the global
hierarchy. Note: does not work on Java type inheritance
relationships.
(distinct)
(distinct coll)
Returns a lazy sequence of the elements of coll with duplicates removed.
Returns a stateful transducer when no collection is provided.
(doall coll)
(doall n coll)
When lazy sequences are produced via functions that have side
effects, any effects other than those needed to produce the first
element in the seq do not occur until the seq is consumed. doall can
be used to force any effects. Walks through the successive nexts of
the seq, retains the head and returns it, thus causing the entire
seq to reside in memory at one time.
(dorun coll)
(dorun n coll)
When lazy sequences are produced via functions that have side
effects, any effects other than those needed to produce the first
element in the seq do not occur until the seq is consumed. dorun can
be used to force any effects. Walks through the successive nexts of
the seq, does not retain the head and returns nil.
(doseq seq-exprs & body)
Repeatedly executes body (presumably for side-effects) with
bindings and filtering as provided by "for". Does not retain
the head of the sequence. Returns nil.
(dosync & exprs)
Runs the exprs (in an implicit do) in a transaction that encompasses
exprs and any nested calls. Starts a transaction if none is already
running on this thread. Any uncaught exception will abort the
transaction and flow out of dosync. The exprs may be run more than
once, but any effects on Refs will be atomic.
(dotimes bindings & body)
bindings => name n
Repeatedly executes body (presumably for side-effects) with name
bound to integers from 0 through n-1.
(doto x & forms)
Evaluates x then calls all of the methods and functions with the
value of x supplied at the front of the given arguments. The forms
are evaluated in order. Returns x.
(doto (new java.util.HashMap) (.put "a" 1) (.put "b" 2))
(drop n)
(drop n coll)
Returns a lazy sequence of all but the first n items in coll.
Returns a stateful transducer when no collection is provided.
(drop-while pred)
(drop-while pred coll)
Returns a lazy sequence of the items in coll starting from the
first item for which (pred item) returns logical false. Returns a
stateful transducer when no collection is provided.
(eduction xform* coll)
Returns a reducible/iterable application of the transducers
to the items in coll. Transducers are applied in order as if
combined with comp. Note that these applications will be
performed every time reduce/iterator is called.
(empty coll)
Returns an empty collection of the same category as coll, or nil
(empty? coll)
Returns true if coll has no items - same as (not (seq coll)).
Please use the idiom (seq x) rather than (not (empty? x))
(ensure ref)
Must be called in a transaction. Protects the ref from modification
by other transactions. Returns the in-transaction-value of
ref. Allows for more concurrency than (ref-set ref @ref)
(error-handler a)
Returns the error-handler of agent a, or nil if there is none.
See set-error-handler!
(eval form)
Evaluates the form data structure (not text!) and returns the result.
(even? n)
Returns true if n is even, throws an exception if n is not an integer
(every-pred p)
(every-pred p1 p2)
(every-pred p1 p2 p3)
(every-pred p1 p2 p3 & ps)
Takes a set of predicates and returns a function f that returns true if all of its
composing predicates return a logical true value against all of its arguments, else it returns
false. Note that f is short-circuiting in that it will stop execution on the first
argument that triggers a logical false result against the original predicates.
(every? pred coll)
Returns true if (pred x) is logical true for every x in coll, else
false.
(ex-data ex)
Returns exception data (a map) if ex is an IExceptionInfo.
Otherwise returns nil.
(extend atype & proto+mmaps)
Implementations of protocol methods can be provided using the extend construct:
(extend AType
AProtocol
{:foo an-existing-fn
:bar (fn [a b] ...)
:baz (fn ([a]...) ([a b] ...)...)}
BProtocol
{...}
...)
extend takes a type/class (or interface, see below), and one or more
protocol + method map pairs. It will extend the polymorphism of the
protocol's methods to call the supplied methods when an AType is
provided as the first argument.
Method maps are maps of the keyword-ized method names to ordinary
fns. This facilitates easy reuse of existing fns and fn maps, for
code reuse/mixins without derivation or composition. You can extend
an interface to a protocol. This is primarily to facilitate interop
with the host (e.g. Java) but opens the door to incidental multiple
inheritance of implementation since a class can inherit from more
than one interface, both of which extend the protocol. It is TBD how
to specify which impl to use. You can extend a protocol on nil.
If you are supplying the definitions explicitly (i.e. not reusing
exsting functions or mixin maps), you may find it more convenient to
use the extend-type or extend-protocol macros.
Note that multiple independent extend clauses can exist for the same
type, not all protocols need be defined in a single extend call.
See also:
extends?, satisfies?, extenders
(extend-protocol p & specs)
Useful when you want to provide several implementations of the same
protocol all at once. Takes a single protocol and the implementation
of that protocol for one or more types. Expands into calls to
extend-type:
(extend-protocol Protocol
AType
(foo [x] ...)
(bar [x y] ...)
BType
(foo [x] ...)
(bar [x y] ...)
AClass
(foo [x] ...)
(bar [x y] ...)
nil
(foo [x] ...)
(bar [x y] ...))
expands into:
(do
(clojure.core/extend-type AType Protocol
(foo [x] ...)
(bar [x y] ...))
(clojure.core/extend-type BType Protocol
(foo [x] ...)
(bar [x y] ...))
(clojure.core/extend-type AClass Protocol
(foo [x] ...)
(bar [x y] ...))
(clojure.core/extend-type nil Protocol
(foo [x] ...)
(bar [x y] ...)))
(extend-type t & specs)
A macro that expands into an extend call. Useful when you are
supplying the definitions explicitly inline, extend-type
automatically creates the maps required by extend. Propagates the
class as a type hint on the first argument of all fns.
(extend-type MyType
Countable
(cnt [c] ...)
Foo
(bar [x y] ...)
(baz ([x] ...) ([x y & zs] ...)))
expands into:
(extend MyType
Countable
{:cnt (fn [c] ...)}
Foo
{:baz (fn ([x] ...) ([x y & zs] ...))
:bar (fn [x y] ...)})
(false? x)
Returns true if x is the value false, false otherwise.
(filter pred)
(filter pred coll)
Returns a lazy sequence of the items in coll for which
(pred item) returns logical true. pred must be free of side-effects.
Returns a transducer when no collection is provided.
(filterv pred coll)
Returns a vector of the items in coll for which
(pred item) returns logical true. pred must be free of side-effects.
(find map key)
Returns the map entry for key, or nil if key not present.
(find-keyword name)
(find-keyword ns name)
Returns a Keyword with the given namespace and name if one already
exists. This function will not intern a new keyword. If the keyword
has not already been interned, it will return nil. Do not use :
in the keyword strings, it will be added automatically.
(find-ns sym)
Returns the namespace named by the symbol or nil if it doesn't exist.
(find-var sym)
Returns the global var named by the namespace-qualified symbol, or
nil if no var with that name.
(first coll)
Returns the first item in the collection. Calls seq on its
argument. If coll is nil, returns nil.
(flatten x)
Takes any nested combination of sequential things (lists, vectors,
etc.) and returns their contents as a single, flat sequence.
(flatten nil) returns an empty sequence.
(float? n)
Returns true if n is a floating point number
(flush)
Flushes the output stream that is the current value of
*out*
(fn & sigs)
params => positional-params* , or positional-params* & next-param
positional-param => binding-form
next-param => binding-form
name => symbol
Defines a function
(fn? x)
Returns true if x implements Fn, i.e. is an object created via fn.
(fnil f x)
(fnil f x y)
(fnil f x y z)
Takes a function f, and returns a function that calls f, replacing
a nil first argument to f with the supplied value x. Higher arity
versions can replace arguments in the second and third
positions (y, z). Note that the function f can take any number of
arguments, not just the one(s) being nil-patched.
(for seq-exprs body-expr)
List comprehension. Takes a vector of one or more
binding-form/collection-expr pairs, each followed by zero or more
modifiers, and yields a lazy sequence of evaluations of expr.
Collections are iterated in a nested fashion, rightmost fastest,
and nested coll-exprs can refer to bindings created in prior
binding-forms. Supported modifiers are: :let [binding-form expr ...],
:while test, :when test.
(take 100 (for [x (range 100000000) y (range 1000000) :while (< y x)] [x y]))
(force x)
If x is a Delay, returns the (possibly cached) value of its expression, else returns x
(format fmt & args)
Formats a string using java.lang.String.format, see java.util.Formatter for format
string syntax
(frequencies coll)
Returns a map from distinct items in coll to the number of times
they appear.
(future & body)
Takes a body of expressions and yields a future object that will
invoke the body in another thread, and will cache the result and
return it on all subsequent calls to deref/@. If the computation has
not yet finished, calls to deref/@ will block, unless the variant of
deref with timeout is used. See also - realized?.
(future-call f)
Takes a function of no args and yields a future object that will
invoke the function in another thread, and will cache the result and
return it on all subsequent calls to deref/@. If the computation has
not yet finished, calls to deref/@ will block, unless the variant
of deref with timeout is used. See also - realized?.
(gen-class & options)
When compiling, generates compiled bytecode for a class with the
given package-qualified :name (which, as all names in these
parameters, can be a string or symbol), and writes the .class file
to the *compile-path* directory. When not compiling, does
nothing. The gen-class construct contains no implementation, as the
implementation will be dynamically sought by the generated class in
functions in an implementing Clojure namespace. Given a generated
class org.mydomain.MyClass with a method named mymethod, gen-class
will generate an implementation that looks for a function named by
(str prefix mymethod) (default prefix: "-") in a
Clojure namespace specified by :impl-ns
(defaults to the current namespace). All inherited methods,
generated methods, and init and main functions (see :methods, :init,
and :main below) will be found similarly prefixed. By default, the
static initializer for the generated class will attempt to load the
Clojure support code for the class as a resource from the classpath,
e.g. in the example case, ``org/mydomain/MyClass__init.class``. This
behavior can be controlled by :load-impl-ns
Note that methods with a maximum of 18 parameters are supported.
In all subsequent sections taking types, the primitive types can be
referred to by their Java names (int, float etc), and classes in the
java.lang package can be used without a package qualifier. All other
classes must be fully qualified.
Options should be a set of key/value pairs, all except for :name are optional:
:name aname
The package-qualified name of the class to be generated
:extends aclass
Specifies the superclass, the non-private methods of which will be
overridden by the class. If not provided, defaults to Object.
:implements [interface ...]
One or more interfaces, the methods of which will be implemented by the class.
:init name
If supplied, names a function that will be called with the arguments
to the constructor. Must return [ [superclass-constructor-args] state]
If not supplied, the constructor args are passed directly to
the superclass constructor and the state will be nil
:constructors {[param-types] [super-param-types], ...}
By default, constructors are created for the generated class which
match the signature(s) of the constructors for the superclass. This
parameter may be used to explicitly specify constructors, each entry
providing a mapping from a constructor signature to a superclass
constructor signature. When you supply this, you must supply an :init
specifier.
:post-init name
If supplied, names a function that will be called with the object as
the first argument, followed by the arguments to the constructor.
It will be called every time an object of this class is created,
immediately after all the inherited constructors have completed.
Its return value is ignored.
:methods [ [name [param-types] return-type], ...]
The generated class automatically defines all of the non-private
methods of its superclasses/interfaces. This parameter can be used
to specify the signatures of additional methods of the generated
class. Static methods can be specified with ^{:static true} in the
signature's metadata. Do not repeat superclass/interface signatures
here.
:main boolean
If supplied and true, a static public main function will be generated. It will
pass each string of the String[] argument as a separate argument to
a function called (str prefix main).
:factory name
If supplied, a (set of) public static factory function(s) will be
created with the given name, and the same signature(s) as the
constructor(s).
:state name
If supplied, a public final instance field with the given name will be
created. You must supply an :init function in order to provide a
value for the state. Note that, though final, the state can be a ref
or agent, supporting the creation of Java objects with transactional
or asynchronous mutation semantics.
:exposes {protected-field-name {:get name :set name}, ...}
Since the implementations of the methods of the generated class
occur in Clojure functions, they have no access to the inherited
protected fields of the superclass. This parameter can be used to
generate public getter/setter methods exposing the protected field(s)
for use in the implementation.
:exposes-methods {super-method-name exposed-name, ...}
It is sometimes necessary to call the superclass' implementation of an
overridden method. Those methods may be exposed and referred in
the new method implementation by a local name.
:prefix string
Default: "-" Methods called e.g. Foo will be looked up in vars called
prefixFoo in the implementing ns.
:impl-ns name
Default: the name of the current ns. Implementations of methods will be
looked up in this namespace.
:load-impl-ns boolean
Default: true. Causes the static initializer for the generated class
to reference the load code for the implementing namespace. Should be
true when implementing-ns is the default, false if you intend to
load the code via some other method.
(gen-interface & options)
When compiling, generates compiled bytecode for an interface with
the given package-qualified :name (which, as all names in these
parameters, can be a string or symbol), and writes the .class file
to the *compile-path* directory. When not compiling, does nothing.
In all subsequent sections taking types, the primitive types can be
referred to by their Java names (int, float etc), and classes in the
java.lang package can be used without a package qualifier. All other
classes must be fully qualified.
Options should be a set of key/value pairs, all except for :name are
optional:
:name aname
The package-qualified name of the class to be generated
:extends [interface ...]
One or more interfaces, which will be extended by this interface.
:methods [ [name [param-types] return-type], ...]
This parameter is used to specify the signatures of the methods of
the generated interface. Do not repeat superinterface signatures
here.
(gensym)
(gensym prefix-string)
Returns a new symbol with a unique name. If a prefix string is
supplied, the name is prefix# where # is some unique number. If
prefix is not supplied, the prefix is 'G__'.
(get-in m ks)
(get-in m ks not-found)
Returns the value in a nested associative structure,
where ks is a sequence of keys. Returns nil if the key
is not present, or the not-found value if supplied.
(get-method multifn dispatch-val)
Given a multimethod and a dispatch value, returns the dispatch fn
that would apply to that value, or nil if none apply and no default
(get-proxy-class & bases)
Takes an optional single class followed by zero or more
interfaces. If not supplied class defaults to Object. Creates an
returns an instance of a proxy class derived from the supplied
classes. The resulting value is cached and used for any subsequent
requests for the same class set. Returns a Class object.
(get-thread-bindings)
Get a map with the Var/value pairs which is currently in effect for the
current thread.
(group-by f coll)
Returns a map of the elements of coll keyed by the result of
f on each element. The value at each key will be a vector of the
corresponding elements, in the order they appeared in coll.
(halt-when pred)
(halt-when pred retf)
Returns a transducer that ends transduction when pred returns true
for an input. When retf is supplied it must be a fn of 2 arguments -
it will be passed the (completed) result so far and the input that
triggered the predicate, and its return value (if it does not throw
an exception) will be the return value of the transducer. If retf
is not supplied, the input that triggered the predicate will be
returned. If the predicate never returns true the transduction is
unaffected.
(hash x)
Returns the hash code of its argument. Note this is the hash code
consistent with =, and thus is different than .hashCode for Integer,
Short, Byte and Clojure collections.
(hash-map)
(hash-map & keyvals)
keyval => key val
Returns a new hash map with supplied mappings. If any keys are
equal, they are handled as if by repeated uses of assoc.
(hash-ordered-coll coll)
Returns the hash code, consistent with =, for an external ordered
collection implementing Iterable.
See http://clojure.org/data_structures#hash for full algorithms.
(hash-unordered-coll coll)
Returns the hash code, consistent with =, for an external unordered
collection implementing Iterable. For maps, the iterator should
return map entries whose hash is computed as
(hash-ordered-coll [k v]).
See http://clojure.org/data_structures#hash for full algorithms.
(ifn? x)
Returns true if x implements IFn. Note that many data structures
(e.g. sets and maps) implement IFn
(import & import-symbols-or-lists)
import-list => (package-symbol class-name-symbols*)
For each name in class-name-symbols, adds a mapping from name to the
class named by package.name to the current namespace. Use :import in the ns
macro in preference to calling this directly.
(in-ns name)
Sets *ns* to the namespace named by the symbol, creating it if needed.
(inc x)
Returns a number one greater than num. Does not auto-promote
longs, will throw on overflow. See also: inc'
(inc' x)
Returns a number one greater than num. Supports arbitrary precision.
See also: inc
(indexed? coll)
Return true if coll implements Indexed, indicating efficient lookup by index
(init-proxy proxy mappings)
Takes a proxy instance and a map of strings (which must
correspond to methods of the proxy superclass/superinterfaces) to
fns (which must take arguments matching the corresponding method,
plus an additional (explicit) first arg corresponding to this, and
sets the proxy's fn map. Returns the proxy.
(inst-ms inst)
Return the number of milliseconds since January 1, 1970, 00:00:00 GMT
(instance? c x)
Evaluates x and tests if it is an instance of the class
c. Returns true or false
(int? x)
Return true if x is a fixed precision integer
(intern ns name)
(intern ns name val)
Finds or creates a var named by the symbol name in the namespace
ns (which can be a symbol or a namespace), setting its root binding
to val if supplied. The namespace must exist. The var will adopt any
metadata from the name symbol. Returns the var.
(into-array aseq)
(into-array type aseq)
Returns an array with components set to the values in aseq. The array's
component type is type if provided, or the type of the first value in
aseq if present, or Object. All values in aseq must be compatible with
the component type. Class objects for the primitive types can be obtained
using, e.g., Integer/TYPE.
(io! & body)
If an io! block occurs in a transaction, throws an
IllegalStateException, else runs body in an implicit do. If the
first expression in body is a literal string, will use that as the
exception message.
(isa? child parent)
(isa? h child parent)
Returns true if (= child parent), or child is directly or indirectly derived from
parent, either via a Java type inheritance relationship or a
relationship established via derive. h must be a hierarchy obtained
from make-hierarchy, if not supplied defaults to the global
hierarchy
(iterate f x)
Returns a lazy sequence of x, (f x), (f (f x)) etc. f must be free of side-effects
(iterator-seq iter)
Returns a seq on a java.util.Iterator. Note that most collections
providing iterators implement Iterable and thus support seq directly.
Seqs cache values, thus iterator-seq should not be used on any
iterator that repeatedly returns the same mutable object.
(juxt f)
(juxt f g)
(juxt f g h)
(juxt f g h & fs)
Takes a set of functions and returns a fn that is the juxtaposition
of those fns. The returned fn takes a variable number of args, and
returns a vector containing the result of applying each fn to the
args (left-to-right).
((juxt a b c) x) => [(a x) (b x) (c x)]
(keep f)
(keep f coll)
Returns a lazy sequence of the non-nil results of (f item). Note,
this means false return values will be included. f must be free of
side-effects. Returns a transducer when no collection is provided.
(keep-indexed f)
(keep-indexed f coll)
Returns a lazy sequence of the non-nil results of (f index item). Note,
this means false return values will be included. f must be free of
side-effects. Returns a stateful transducer when no collection is
provided.
(key e)
Returns the key of the map entry.
(keys map)
Returns a sequence of the map's keys, in the same order as (seq map).
(last coll)
Return the last item in coll, in linear time
(lazy-cat & colls)
Expands to code which yields a lazy sequence of the concatenation
of the supplied colls. Each coll expr is not evaluated until it is
needed.
(lazy-cat xs ys zs) === (concat (lazy-seq xs) (lazy-seq ys) (lazy-seq zs))
(lazy-seq & body)
Takes a body of expressions that returns an ISeq or nil, and yields
a Seqable object that will invoke the body only the first time seq
is called, and will cache the result and return it on all subsequent
seq calls. See also - realized?
(let bindings & body)
binding => binding-form init-expr
Evaluates the exprs in a lexical context in which the symbols in
the binding-forms are bound to their respective init-exprs or parts
therein.
(letfn fnspecs & body)
fnspec ==> (fname [params*] exprs) or (fname ([params*] exprs)+)
Takes a vector of function specs and a body, and generates a set of
bindings of functions to their names. All of the names are available
in all of the definitions of the functions, as well as the body.
(line-seq rdr)
Returns the lines of text from rdr as a lazy sequence of strings.
rdr must implement java.io.BufferedReader.
(list? x)
Returns true if x implements IPersistentList
(load & paths)
Loads Clojure code from resources in classpath. A path is interpreted as
classpath-relative if it begins with a slash or relative to the root
directory for the current namespace otherwise.
(load-file name)
Sequentially read and evaluate the set of forms contained in the file.
(load-reader rdr)
Sequentially read and evaluate the set of forms contained in the
stream/file
(load-string s)
Sequentially read and evaluate the set of forms contained in the
string
(loaded-libs)
Returns a sorted set of symbols naming the currently loaded libs
(locking x & body)
Executes exprs in an implicit do, while holding the monitor of x.
Will release the monitor of x in all circumstances.
(loop bindings & body)
Evaluates the exprs in a lexical context in which the symbols in
the binding-forms are bound to their respective init-exprs or parts
therein. Acts as a recur target.
(macroexpand form)
Repeatedly calls macroexpand-1 on form until it no longer
represents a macro form, then returns it. Note neither
macroexpand-1 nor macroexpand expand macros in subforms.
(make-array type len)
(make-array type dim & more-dims)
Creates and returns an array of instances of the specified class of
the specified dimension(s). Note that a class object is required.
Class objects can be obtained by using their imported or
fully-qualified name. Class objects for the primitive types can be
obtained using, e.g., Integer/TYPE.
(map f)
(map f coll)
(map f c1 c2)
(map f c1 c2 c3)
(map f c1 c2 c3 & colls)
Returns a lazy sequence consisting of the result of applying f to
the set of first items of each coll, followed by applying f to the
set of second items in each coll, until any one of the colls is
exhausted. Any remaining items in other colls are ignored. Function
f should accept number-of-colls arguments. Returns a transducer when
no collection is provided.
(map-indexed f)
(map-indexed f coll)
Returns a lazy sequence consisting of the result of applying f to 0
and the first item of coll, followed by applying f to 1 and the second
item in coll, etc, until coll is exhausted. Thus function f should
accept 2 arguments, index and item. Returns a stateful transducer when
no collection is provided.
(map? x)
Return true if x implements IPersistentMap
(mapcat f)
(mapcat f & colls)
Returns the result of applying concat to the result of applying map
to f and colls. Thus function f should return a collection. Returns
a transducer when no collections are provided
(mapv f coll)
(mapv f c1 c2)
(mapv f c1 c2 c3)
(mapv f c1 c2 c3 & colls)
Returns a vector consisting of the result of applying f to the
set of first items of each coll, followed by applying f to the set
of second items in each coll, until any one of the colls is
exhausted. Any remaining items in other colls are ignored. Function
f should accept number-of-colls arguments.
(memfn name & args)
Expands into code that creates a fn that expects to be passed an
object and any args and calls the named instance method on the
object passing the args. Use when you want to treat a Java method as
a first-class fn. name may be type-hinted with the method receiver's
type in order to avoid reflective calls.
(memoize f)
Returns a memoized version of a referentially transparent function. The
memoized version of the function keeps a cache of the mapping from arguments
to results and, when calls with the same arguments are repeated often, has
higher performance at the expense of higher memory use.
(merge & maps)
Returns a map that consists of the rest of the maps conj-ed onto
the first. If a key occurs in more than one map, the mapping from
the latter (left-to-right) will be the mapping in the result.
(merge-with f & maps)
Returns a map that consists of the rest of the maps conj-ed onto
the first. If a key occurs in more than one map, the mapping(s)
from the latter (left-to-right) will be combined with the mapping in
the result by calling (f val-in-result val-in-latter).
(meta obj)
Returns the metadata of obj, returns nil if there is no metadata.
(methods multifn)
Given a multimethod, returns a map of dispatch values -> dispatch fns
(mix-collection-hash hash-basis count)
Mix final collection hash for ordered or unordered collections.
hash-basis is the combined collection hash, count is the number
of elements included in the basis. Note this is the hash code
consistent with =, different from .hashCode.
See http://clojure.org/data_structures#hash for full algorithms.
(mod num div)
Modulus of num and div. Truncates toward negative infinity.
(name x)
Returns the name String of a string, symbol or keyword.
(namespace x)
Returns the namespace String of a symbol or keyword, or nil if not present.
(nat-int? x)
Return true if x is a non-negative fixed precision integer
(neg-int? x)
Return true if x is a negative fixed precision integer
(neg? num)
Returns true if num is less than zero, else false
(newline)
Writes a platform-specific newline to *out*
(next coll)
Returns a seq of the items after the first. Calls seq on its
argument. If there are no more items, returns nil.
(nil? x)
Returns true if x is nil, false otherwise.
(not x)
Returns true if x is logical false, false otherwise.
(ns name docstring? attr-map? references*)
Sets *ns* to the namespace named by name (unevaluated), creating it
if needed. references can be zero or more of: (:refer-clojure ...)
(:require ...) (:use ...) (:import ...) (:load ...) (:gen-class)
with the syntax of refer-clojure/require/use/import/load/gen-class
respectively, except the arguments are unevaluated and need not be
quoted. (:gen-class ...), when supplied, defaults to :name
corresponding to the ns name, :main true, :impl-ns same as ns, and
:init-impl-ns true. All options of gen-class are
supported. The :gen-class directive is ignored when not
compiling. If :gen-class is not supplied, when compiled only an
nsname__init.class will be generated. If :refer-clojure is not used, a
default (refer 'clojure.core) is used. Use of ns is preferred to
individual calls to in-ns/require/use/import:
(ns foo.bar
(:refer-clojure :exclude [ancestors printf])
(:require (clojure.contrib sql combinatorics))
(:use (my.lib this that))
(:import (java.util Date Timer Random)
(java.sql Connection Statement)))
(ns-map ns)
Returns a map of all the mappings for the namespace.
(ns-publics ns)
Returns a map of the public intern mappings for the namespace.
(ns-resolve ns sym)
(ns-resolve ns env sym)
Returns the var or Class to which a symbol will be resolved in the
namespace (unless found in the environment), else nil. Note that
if the symbol is fully qualified, the var/Class to which it resolves
need not be present in the namespace.
(nth coll index)
(nth coll index not-found)
Returns the value at the index. get returns nil if index out of
bounds, nth throws an exception unless not-found is supplied. nth
also works for strings, Java arrays, regex Matchers and Lists, and,
in O(n) time, for sequences.
(odd? n)
Returns true if n is odd, throws an exception if n is not an integer
(or)
(or x)
(or x & next)
Evaluates exprs one at a time, from left to right. If a form
returns a logical true value, or returns that value and doesn't
evaluate any of the other expressions, otherwise it returns the
value of the last expression. (or) returns nil.
(parents tag)
(parents h tag)
Returns the immediate parents of tag, either via a Java type
inheritance relationship or a relationship established via derive. h
must be a hierarchy obtained from make-hierarchy, if not supplied
defaults to the global hierarchy
(partition n coll)
(partition n step coll)
(partition n step pad coll)
Returns a lazy sequence of lists of n items each, at offsets step
apart. If step is not supplied, defaults to n, i.e. the partitions
do not overlap. If a pad collection is supplied, use its elements as
necessary to complete last partition upto n items. In case there are
not enough padding elements, return a partition with less than n items.
(partition-by f)
(partition-by f coll)
Applies f to each value in coll, splitting it each time f returns a
new value. Returns a lazy seq of partitions. Returns a stateful
transducer when no collection is provided.
(pcalls & fns)
Executes the no-arg fns in parallel, returning a lazy sequence of
their values
(peek coll)
For a list or queue, same as first, for a vector, same as, but much
more efficient than, last. If the collection is empty, returns nil.
(persistent! coll)
Returns a new, persistent version of the transient collection, in
constant time. The transient collection cannot be used after this
call, any such use will throw an exception.
(pmap f coll)
(pmap f coll & colls)
Like map, except f is applied in parallel. Semi-lazy in that the
parallel computation stays ahead of the consumption, but doesn't
realize the entire result unless required. Only useful for
computationally intensive functions where the time of f dominates
the coordination overhead.
(pop coll)
For a list or queue, returns a new list/queue without the first
item, for a vector, returns a new vector without the last item. If
the collection is empty, throws an exception. Note - not the same
as next/butlast.
(pop! coll)
Removes the last item from a transient vector. If
the collection is empty, throws an exception. Returns coll
(pop-thread-bindings)
Pop one set of bindings pushed with push-binding before. It is an error to
pop bindings without pushing before.
(pos-int? x)
Return true if x is a positive fixed precision integer
(pos? num)
Returns true if num is greater than zero, else false
(pr)
(pr x)
(pr x & more)
Prints the object(s) to the output stream that is the current value
of *out*. Prints the object(s), separated by spaces if there is
more than one. By default, pr and prn print in a way that objects
can be read by the reader
(prefers multifn)
Given a multimethod, returns a map of preferred value -> set of other values
(print & more)
Prints the object(s) to the output stream that is the current value
of *out*. print and println produce output for human consumption.
(prn & more)
Same as pr followed by (newline). Observes *flush-on-newline*
(promise)
Returns a promise object that can be read with deref/@, and set,
once only, with deliver. Calls to deref/@ prior to delivery will
block, unless the variant of deref with timeout is used. All
subsequent derefs will return the same delivered value without
blocking. See also - realized?.
(proxy class-and-interfaces args & fs)
class-and-interfaces - a vector of class names
args - a (possibly empty) vector of arguments to the superclass
constructor.
f => (name [params*] body) or
(name ([params*] body) ([params+] body) ...)
Expands to code which creates a instance of a proxy class that
implements the named class/interface(s) by calling the supplied
fns. A single class, if provided, must be first. If not provided it
defaults to Object.
The interfaces names must be valid interface types. If a method fn
is not provided for a class method, the superclass methd will be
called. If a method fn is not provided for an interface method, an
UnsupportedOperationException will be thrown should it be
called. Method fns are closures and can capture the environment in
which proxy is called. Each method fn takes an additional implicit
first arg, which is bound to 'this. Note that while method fns can
be provided to override protected methods, they have no other access
to protected members, nor to super, as these capabilities cannot be
proxied.
(push-thread-bindings bindings)
WARNING: This is a low-level function. Prefer high-level macros like
binding where ever possible.
Takes a map of Var/value pairs. Binds each Var to the associated value for
the current thread. Each call *MUST* be accompanied by a matching call to
pop-thread-bindings wrapped in a try-finally!
(push-thread-bindings bindings)
(try
...
(finally
(pop-thread-bindings)))
(pvalues & exprs)
Returns a lazy sequence of the values of the exprs, which are
evaluated in parallel
(rand)
(rand n)
Returns a random floating point number between 0 (inclusive) and
n (default 1) (exclusive).
(rand-int n)
Returns a random integer between 0 (inclusive) and n (exclusive).
(rand-nth coll)
Return a random element of the (sequential) collection. Will have
the same performance characteristics as nth for the given
collection.
(range)
(range end)
(range start end)
(range start end step)
Returns a lazy seq of nums from start (inclusive) to end
(exclusive), by step, where start defaults to 0, step to 1, and end to
infinity. When step is equal to 0, returns an infinite sequence of
start. When start is equal to end, returns empty list.
(re-find m)
(re-find re s)
Returns the next regex match, if any, of string to pattern, using
java.util.regex.Matcher.find(). Uses re-groups to return the
groups.
(re-groups m)
Returns the groups from the most recent match/find. If there are no
nested groups, returns a string of the entire match. If there are
nested groups, returns a vector of the groups, the first element
being the entire match.
(re-matcher re s)
Returns an instance of java.util.regex.Matcher, for use, e.g. in
re-find.
(re-matches re s)
Returns the match, if any, of string to pattern, using
java.util.regex.Matcher.matches(). Uses re-groups to return the
groups.
(re-pattern s)
Returns an instance of java.util.regex.Pattern, for use, e.g. in
re-matcher.
(re-seq re s)
Returns a lazy sequence of successive matches of pattern in string,
using java.util.regex.Matcher.find(), each such match processed with
re-groups.
(read)
(read stream)
(read stream eof-error? eof-value)
(read stream eof-error? eof-value recursive?)
(read opts stream)
Reads the next object from stream, which must be an instance of
java.io.PushbackReader or some derivee. stream defaults to the
current value of *in*.
Opts is a persistent map with valid keys:
:read-cond - :allow to process reader conditionals, or
:preserve to keep all branches
:features - persistent set of feature keywords for reader conditionals
:eof - on eof, return value unless :eofthrow, then throw.
if not specified, will throw
Note that read can execute code (controlled by *read-eval*),
and as such should be used only with trusted sources.
For data structure interop use clojure.edn/read
(read-line)
Reads the next line from stream that is the current value of *in* .
(read-string s)
(read-string opts s)
Reads one object from the string s. Optionally include reader
options, as specified in read.
Note that read-string can execute code (controlled by *read-eval*),
and as such should be used only with trusted sources.
For data structure interop use clojure.edn/read-string
(realized? x)
Returns true if a value has been produced for a promise, delay, future or lazy sequence.
(reduce f coll)
(reduce f val coll)
f should be a function of 2 arguments. If val is not supplied,
returns the result of applying f to the first 2 items in coll, then
applying f to that result and the 3rd item, etc. If coll contains no
items, f must accept no arguments as well, and reduce returns the
result of calling f with no arguments. If coll has only 1 item, it
is returned and f is not called. If val is supplied, returns the
result of applying f to val and the first item in coll, then
applying f to that result and the 2nd item, etc. If coll contains no
items, returns val and f is not called.
(reduce-kv f init coll)
Reduces an associative collection. f should be a function of 3
arguments. Returns the result of applying f to init, the first key
and the first value in coll, then applying f to that result and the
2nd key and value, etc. If coll contains no entries, returns init
and f is not called. Note that reduce-kv is supported on vectors,
where the keys will be the ordinals.
(reduced x)
Wraps x in a way such that a reduce will terminate with the value x
(reduced? x)
Returns true if x is the result of a call to reduced
(ref x)
(ref x & options)
Creates and returns a Ref with an initial value of x and zero or
more options (in any order):
:meta metadata-map
:validator validate-fn
:min-history (default 0)
:max-history (default 10)
If metadata-map is supplied, it will become the metadata on the
ref. validate-fn must be nil or a side-effect-free fn of one
argument, which will be passed the intended new state on any state
change. If the new state is unacceptable, the validate-fn should
return false or throw an exception. validate-fn will be called on
transaction commit, when all refs have their final values.
Normally refs accumulate history dynamically as needed to deal with
read demands. If you know in advance you will need history you can
set :min-history to ensure it will be available when first needed (instead
of after a read fault). History is limited, and the limit can be set
with :max-history.
(ref-set ref val)
Must be called in a transaction. Sets the value of ref.
Returns val.
(refer ns-sym & filters)
refers to all public vars of ns, subject to filters.
filters can include at most one each of:
:exclude list-of-symbols
:only list-of-symbols
:rename map-of-fromsymbol-tosymbol
For each public interned var in the namespace named by the symbol,
adds a mapping from the name of the var to the var to the current
namespace. Throws an exception if name is already mapped to
something else in the current namespace. Filters can be used to
select a subset, via inclusion or exclusion, or to provide a mapping
to a symbol different from the var's name, in order to prevent
clashes. Use :use in the ns macro in preference to calling this directly.
(reify & opts+specs)
reify is a macro with the following structure:
(reify options* specs*)
Currently there are no options.
Each spec consists of the protocol or interface name followed by zero
or more method bodies:
protocol-or-interface-or-Object
(methodName [args+] body)*
Methods should be supplied for all methods of the desired
protocol(s) and interface(s). You can also define overrides for
methods of Object. Note that the first parameter must be supplied to
correspond to the target object ('this' in Java parlance). Thus
methods for interfaces will take one more argument than do the
interface declarations. Note also that recur calls to the method
head should *not* pass the target object, it will be supplied
automatically and can not be substituted.
The return type can be indicated by a type hint on the method name,
and arg types can be indicated by a type hint on arg names. If you
leave out all hints, reify will try to match on same name/arity
method in the protocol(s)/interface(s) - this is preferred. If you
supply any hints at all, no inference is done, so all hints (or
default of Object) must be correct, for both arguments and return
type. If a method is overloaded in a protocol/interface, multiple
independent method definitions must be supplied. If overloaded with
same arity in an interface you must specify complete hints to
disambiguate - a missing hint implies Object.
recur works to method heads The method bodies of reify are lexical
closures, and can refer to the surrounding local scope:
(str (let [f "foo"]
(reify Object
(toString [this] f))))
== "foo"
(seq (let [f "foo"]
(reify clojure.lang.Seqable
(seq [this] (seq f)))))
== (\f \o \o))
reify always implements clojure.lang.IObj and transfers meta
data of the form to the created object.
(meta ^{:k :v} (reify Object (toString [this] "foo")))
== {:k :v}
(release-pending-sends)
Normally, actions sent directly or indirectly during another action
are held until the action completes (changes the agent's
state). This function can be used to dispatch any pending sent
actions immediately. This has no impact on actions sent during a
transaction, which are still held until commit. If no action is
occurring, does nothing. Returns the number of actions dispatched.
(remove pred)
(remove pred coll)
Returns a lazy sequence of the items in coll for which
(pred item) returns logical false. pred must be free of side-effects.
Returns a transducer when no collection is provided.
(remove-ns sym)
Removes the namespace named by the symbol. Use with caution.
Cannot be used to remove the clojure namespace.
(repeatedly f)
(repeatedly n f)
Takes a function of no args, presumably with side effects, and
returns an infinite (or length n if supplied) lazy sequence of calls
to it
(replace smap)
(replace smap coll)
Given a map of replacement pairs and a vector/collection, returns a
vector/seq with any elements = a key in smap replaced with the
corresponding val in smap. Returns a transducer when no collection
is provided.
(replicate n x)
DEPRECATED: Use 'repeat' instead.
Returns a lazy seq of n xs.
(require & args)
Loads libs, skipping any that are already loaded. Each argument is
either a libspec that identifies a lib, a prefix list that identifies
multiple libs whose names share a common prefix, or a flag that modifies
how all the identified libs are loaded. Use :require in the ns macro
in preference to calling this directly.
Libs
A 'lib' is a named set of resources in classpath whose contents define a
library of Clojure code. Lib names are symbols and each lib is associated
with a Clojure namespace and a Java package that share its name. A lib's
name also locates its root directory within classpath using Java's
package name to classpath-relative path mapping. All resources in a lib
should be contained in the directory structure under its root directory.
All definitions a lib makes should be in its associated namespace.
'require loads a lib by loading its root resource. The root resource path
is derived from the lib name in the following manner:
Consider a lib named by the symbol 'x.y.z; it has the root directory
<classpath>/x/y/, and its root resource is <classpath>/x/y/z.clj, or
<classpath>/x/y/z.cljc if <classpath>/x/y/z.clj does not exist. The
root resource should contain code to create the lib's
namespace (usually by using the ns macro) and load any additional
lib resources.
Libspecs
A libspec is a lib name or a vector containing a lib name followed by
options expressed as sequential keywords and arguments.
Recognized options:
:as takes a symbol as its argument and makes that symbol an alias to the
lib's namespace in the current namespace.
:refer takes a list of symbols to refer from the namespace or the :all
keyword to bring in all public vars.
Prefix Lists
It's common for Clojure code to depend on several libs whose names have
the same prefix. When specifying libs, prefix lists can be used to reduce
repetition. A prefix list contains the shared prefix followed by libspecs
with the shared prefix removed from the lib names. After removing the
prefix, the names that remain must not contain any periods.
Flags
A flag is a keyword.
Recognized flags: :reload, :reload-all, :verbose
:reload forces loading of all the identified libs even if they are
already loaded
:reload-all implies :reload and also forces loading of all libs that the
identified libs directly or indirectly load via require or use
:verbose triggers printing information about each load, alias, and refer
Example:
The following would load the libraries clojure.zip and clojure.set
abbreviated as 's'.
(require '(clojure zip [set :as s]))
(reset! atom newval)
Sets the value of atom to newval without regard for the
current value. Returns newval.
(reset-vals! atom newval)
Sets the value of atom to newval. Returns [old new], the value of the
atom before and after the reset.
(rest coll)
Returns a possibly empty seq of the items after the first. Calls seq on its
argument.
(restart-agent a new-state & options)
When an agent is failed, changes the agent state to new-state and
then un-fails the agent so that sends are allowed again. If
a :clear-actions true option is given, any actions queued on the
agent that were being held while it was failed will be discarded,
otherwise those held actions will proceed. The new-state must pass
the validator if any, or restart will throw an exception and the
agent will remain failed with its old state and error. Watchers, if
any, will NOT be notified of the new state. Throws an exception if
the agent is not failed.
(resultset-seq rs)
Creates and returns a lazy sequence of structmaps corresponding to
the rows in the java.sql.ResultSet rs
(reverse coll)
Returns a seq of the items in coll in reverse order. Not lazy.
(rseq rev)
Returns, in constant time, a seq of the items in rev (which
can be a vector or sorted-map), in reverse order. If rev is empty returns nil
(run! proc coll)
Runs the supplied procedure (via reduce), for purposes of side
effects, on successive items in the collection. Returns nil
(send a f & args)
Dispatch an action to an agent. Returns the agent immediately.
Subsequently, in a thread from a thread pool, the state of the agent
will be set to the value of:
(apply action-fn state-of-agent args)
(send-off a f & args)
Dispatch a potentially blocking action to an agent. Returns the
agent immediately. Subsequently, in a separate thread, the state of
the agent will be set to the value of:
(apply action-fn state-of-agent args)
(send-via executor a f & args)
Dispatch an action to an agent. Returns the agent immediately.
Subsequently, in a thread supplied by executor, the state of the agent
will be set to the value of:
(apply action-fn state-of-agent args)
(seq coll)
Returns a seq on the collection. If the collection is
empty, returns nil. (seq nil) returns nil. seq also works on
Strings, native Java arrays (of reference types) and any objects
that implement Iterable. Note that seqs cache values, thus seq
should not be used on any Iterable whose iterator repeatedly
returns the same mutable object.
(seq? x)
Return true if x implements ISeq
(seqable? x)
Return true if the seq function is supported for x
(seque s)
(seque n-or-q s)
Creates a queued seq on another (presumably lazy) seq s. The queued
seq will produce a concrete seq in the background, and can get up to
n items ahead of the consumer. n-or-q can be an integer n buffer
size, or an instance of java.util.concurrent BlockingQueue. Note
that reading from a seque can block if the reader gets ahead of the
producer.
(sequence coll)
(sequence xform coll)
(sequence xform coll & colls)
Coerces coll to a (possibly empty) sequence, if it is not already
one. Will not force a lazy seq. (sequence nil) yields (), When a
transducer is supplied, returns a lazy sequence of applications of
the transform to the items in coll(s), i.e. to the set of first
items of each coll, followed by the set of second
items in each coll, until any one of the colls is exhausted. Any
remaining items in other colls are ignored. The transform should accept
number-of-colls arguments
(set coll)
Returns a set of the distinct elements of coll.
(set-error-handler! a handler-fn)
Sets the error-handler of agent a to handler-fn. If an action
being run by the agent throws an exception or doesn't pass the
validator fn, handler-fn will be called with two arguments: the
agent and the exception.
(set-error-mode! a mode-keyword)
Sets the error-mode of agent a to mode-keyword, which must be
either :fail or :continue. If an action being run by the agent
throws an exception or doesn't pass the validator fn, an
error-handler may be called (see set-error-handler!), after which,
if the mode is :continue, the agent will continue as if neither the
action that caused the error nor the error itself ever happened.
If the mode is :fail, the agent will become failed and will stop
accepting new 'send' and 'send-off' actions, and any previously
queued actions will be held until a 'restart-agent'. Deref will
still work, returning the state of the agent before the error.
(set-validator! iref validator-fn)
Sets the validator-fn for a var/ref/agent/atom. validator-fn must be nil or a
side-effect-free fn of one argument, which will be passed the intended
new state on any state change. If the new state is unacceptable, the
validator-fn should return false or throw an exception. If the current state (root
value if var) is not acceptable to the new validator, an exception
will be thrown and the validator will not be changed.
(set? x)
Returns true if x implements IPersistentSet
(shutdown-agents)
Initiates a shutdown of the thread pools that back the agent
system. Running actions will complete, but no new actions will be
accepted
(slurp f & opts)
Opens a reader on f and reads all its contents, returning a string.
See clojure.java.io/reader for a complete list of supported arguments.
(some pred coll)
Returns the first logical true value of (pred x) for any x in coll,
else nil. One common idiom is to use a set as pred, for example
this will return :fred if :fred is in the sequence, otherwise nil:
(some #{:fred} coll)
(some-> expr & forms)
When expr is not nil, threads it into the first form (via ->),
and when that result is not nil, through the next etc
(some->> expr & forms)
When expr is not nil, threads it into the first form (via ->>),
and when that result is not nil, through the next etc
(some-fn p)
(some-fn p1 p2)
(some-fn p1 p2 p3)
(some-fn p1 p2 p3 & ps)
Takes a set of predicates and returns a function f that returns the first logical true value
returned by one of its composing predicates against any of its arguments, else it returns
logical false. Note that f is short-circuiting in that it will stop execution on the first
argument that triggers a logical true result against the original predicates.
(some? x)
Returns true if x is not nil, false otherwise.
(sort coll)
(sort comp coll)
Returns a sorted sequence of the items in coll. If no comparator is
supplied, uses compare. comparator must implement
java.util.Comparator. Guaranteed to be stable: equal elements will
not be reordered. If coll is a Java array, it will be modified. To
avoid this, sort a copy of the array.
(sort-by keyfn coll)
(sort-by keyfn comp coll)
Returns a sorted sequence of the items in coll, where the sort
order is determined by comparing (keyfn item). If no comparator is
supplied, uses compare. comparator must implement
java.util.Comparator. Guaranteed to be stable: equal elements will
not be reordered. If coll is a Java array, it will be modified. To
avoid this, sort a copy of the array.
(sorted-map & keyvals)
keyval => key val
Returns a new sorted map with supplied mappings. If any keys are
equal, they are handled as if by repeated uses of assoc.
(sorted-map-by comparator & keyvals)
keyval => key val
Returns a new sorted map with supplied mappings, using the supplied
comparator. If any keys are equal, they are handled as if by
repeated uses of assoc.
(sorted-set & keys)
Returns a new sorted set with supplied keys. Any equal keys are
handled as if by repeated uses of conj.
(sorted-set-by comparator & keys)
Returns a new sorted set with supplied keys, using the supplied
comparator. Any equal keys are handled as if by repeated uses of
conj.
(spit f content & options)
Opposite of slurp. Opens f with writer, writes content, then
closes f. Options passed to clojure.java.io/writer.
(str)
(str x)
(str x & ys)
With no args, returns the empty string. With one arg x, returns
x.toString(). (str nil) returns the empty string. With more than
one arg, returns the concatenation of the str values of the args.
(struct s & vals)
Returns a new structmap instance with the keys of the
structure-basis. vals must be supplied for basis keys in order -
where values are not supplied they will default to nil.
(struct-map s & inits)
Returns a new structmap instance with the keys of the
structure-basis. keyvals may contain all, some or none of the basis
keys - where values are not supplied they will default to nil.
keyvals can also contain keys not in the basis.
(subvec v start)
(subvec v start end)
Returns a persistent vector of the items in vector from
start (inclusive) to end (exclusive). If end is not supplied,
defaults to (count vector). This operation is O(1) and very fast, as
the resulting vector shares structure with the original and no
trimming is done.
(supers class)
Returns the immediate and indirect superclasses and interfaces of c, if any
(sync flags-ignored-for-now & body)
transaction-flags => TBD, pass nil for now
Runs the exprs (in an implicit do) in a transaction that encompasses
exprs and any nested calls. Starts a transaction if none is already
running on this thread. Any uncaught exception will abort the
transaction and flow out of sync. The exprs may be run more than
once, but any effects on Refs will be atomic.
(take n)
(take n coll)
Returns a lazy sequence of the first n items in coll, or all items if
there are fewer than n. Returns a stateful transducer when
no collection is provided.
(take-last n coll)
Returns a seq of the last n items in coll. Depending on the type
of coll may be no better than linear time. For vectors, see also subvec.
(take-while pred)
(take-while pred coll)
Returns a lazy sequence of successive items from coll while
(pred item) returns logical true. pred must be free of side-effects.
Returns a transducer when no collection is provided.
(test v)
test [v] finds fn at key :test in var metadata and calls it,
presuming failure will throw exception
(the-ns x)
If passed a namespace, returns it. Else, when passed a symbol,
returns the namespace named by it, throwing an exception if not
found.
(thread-bound? & vars)
Returns true if all of the vars provided as arguments have thread-local bindings.
Implies that set!'ing the provided vars will succeed. Returns true if no vars are provided.
(time expr)
Evaluates expr and prints the time it took. Returns the value of
expr.
(to-array coll)
Returns an array of Objects containing the contents of coll, which
can be any Collection. Maps to java.util.Collection.toArray().
(to-array-2d coll)
Returns a (potentially-ragged) 2-dimensional array of Objects
containing the contents of coll, which can be any Collection of any
Collection.
(trampoline f)
(trampoline f & args)
trampoline can be used to convert algorithms requiring mutual
recursion without stack consumption. Calls f with supplied args, if
any. If f returns a fn, calls that fn with no arguments, and
continues to repeat, until the return value is not a fn, then
returns that non-fn value. Note that if you want to return a fn as a
final value, you must wrap it in some data structure and unpack it
after trampoline returns.
(transduce xform f coll)
(transduce xform f init coll)
reduce with a transformation of f (xf). If init is not
supplied, (f) will be called to produce it. f should be a reducing
step function that accepts both 1 and 2 arguments, if it accepts
only 2 you can add the arity-1 with 'completing'. Returns the result
of applying (the transformed) xf to init and the first item in coll,
then applying xf to that result and the 2nd item, etc. If coll
contains no items, returns init and f is not called. Note that
certain transforms may inject or skip items.
(transient coll)
Returns a new, transient version of the collection, in constant time.
(tree-seq branch? children root)
Returns a lazy sequence of the nodes in a tree, via a depth-first walk.
branch? must be a fn of one arg that returns true if passed a node
that can have children (but may not). children must be a fn of one
arg that returns a sequence of the children. Will only be called on
nodes for which branch? returns true. Root is the root node of the
tree.
(true? x)
Returns true if x is the value true, false otherwise.
(type x)
Returns the :type metadata of x, or its Class if none
(unchecked-add x y)
Returns the sum of x and y, both long.
Note - uses a primitive operator subject to overflow.
(unchecked-dec x)
Returns a number one less than x, a long.
Note - uses a primitive operator subject to overflow.
(unchecked-dec-int x)
Returns a number one less than x, an int.
Note - uses a primitive operator subject to overflow.
(unchecked-inc x)
Returns a number one greater than x, a long.
Note - uses a primitive operator subject to overflow.
(unchecked-inc-int x)
Returns a number one greater than x, an int.
Note - uses a primitive operator subject to overflow.
(unchecked-multiply x y)
Returns the product of x and y, both long.
Note - uses a primitive operator subject to overflow.
(unchecked-negate x)
Returns the negation of x, a long.
Note - uses a primitive operator subject to overflow.
(unchecked-subtract x y)
Returns the difference of x and y, both long.
Note - uses a primitive operator subject to overflow.
(underive tag parent)
(underive h tag parent)
Removes a parent/child relationship between parent and
tag. h must be a hierarchy obtained from make-hierarchy, if not
supplied defaults to, and modifies, the global hierarchy.
(update-in m ks f & args)
'Updates' a value in a nested associative structure, where ks is a
sequence of keys and f is a function that will take the old value
and any supplied args and return the new value, and returns a new
nested structure. If any levels do not exist, hash-maps will be
created.
(update-proxy proxy mappings)
Takes a proxy instance and a map of strings (which must
correspond to methods of the proxy superclass/superinterfaces) to
fns (which must take arguments matching the corresponding method,
plus an additional (explicit) first arg corresponding to this, and
updates (via assoc) the proxy's fn map. nil can be passed instead of
a fn, in which case the corresponding method will revert to the
default behavior. Note that this function can be used to update the
behavior of an existing instance without changing its identity.
Returns the proxy.
(uri? x)
Return true if x is a java.net.URI
(use & args)
Like 'require, but also refers to each lib's namespace using
clojure.core/refer. Use :use in the ns macro in preference to calling
this directly.
'use accepts additional options in libspecs: :exclude, :only, :rename.
The arguments and semantics for :exclude, :only, and :rename are the same
as those documented for clojure.core/refer.
(uuid? x)
Return true if x is a java.util.UUID
(val e)
Returns the value in the map entry.
(vals map)
Returns a sequence of the map's values, in the same order as (seq map).
(var-set x val)
Sets the value in the var object to val. The var must be
thread-locally bound.
(var? v)
Returns true if v is of type clojure.lang.Var
(vary-meta obj f & args)
Returns an object of the same type and value as obj, with
(apply f (meta obj) args) as its metadata.
(vec coll)
Creates a new vector containing the contents of coll. Java arrays
will be aliased and should not be modified.
(vector-of t)
(vector-of t & elements)
Creates a new vector of a single primitive type t, where t is one
of :int :long :float :double :byte :short :char or :boolean. The
resulting vector complies with the interface of vectors in general,
but stores the values unboxed internally.
Optionally takes one or more elements to populate the vector.
(vector? x)
Return true if x implements IPersistentVector
(volatile! val)
Creates and returns a Volatile with an initial value of val.
(vreset! vol newval)
Sets the value of volatile to newval without regard for the
current value. Returns newval.
(vswap! vol f & args)
Non-atomically swaps the value of the volatile as if:
(apply f current-value-of-vol args). Returns the value that
was swapped in.
(when-let bindings & body)
bindings => binding-form test
When test is true, evaluates body with binding-form bound to the value of test
(when-some bindings & body)
bindings => binding-form test
When test is not nil, evaluates body with binding-form bound to the
value of test
(while test & body)
Repeatedly executes body while test expression is true. Presumes
some side-effect will cause test to become false/nil. Returns nil
(with-bindings binding-map & body)
Takes a map of Var/value pairs. Installs for the given Vars the associated
values as thread-local bindings. Then executes body. Pops the installed
bindings after body was evaluated. Returns the value of body.
(with-bindings* binding-map f & args)
Takes a map of Var/value pairs. Installs for the given Vars the associated
values as thread-local bindings. Then calls f with the supplied arguments.
Pops the installed bindings after f returned. Returns whatever f returns.
(with-in-str s & body)
Evaluates body in a context in which *in* is bound to a fresh
StringReader initialized with the string s.
(with-local-vars name-vals-vec & body)
varbinding=> symbol init-expr
Executes the exprs in a context in which the symbols are bound to
vars with per-thread bindings to the init-exprs. The symbols refer
to the var objects themselves, and must be accessed with var-get and
var-set
(with-meta obj m)
Returns an object of the same type and value as obj, with
map m as its metadata.
(with-open bindings & body)
bindings => [name init ...]
Evaluates body in a try expression with names bound to the values
of the inits, and a finally clause that calls (.close name) on each
name in reverse order.
(with-out-str & body)
Evaluates exprs in a context in which *out* is bound to a fresh
StringWriter. Returns the string created by any nested printing
calls.
(with-precision precision & exprs)
Sets the precision and rounding mode to be used for BigDecimal operations.
Usage: (with-precision 10 (/ 1M 3))
or: (with-precision 10 :rounding HALF_DOWN (/ 1M 3))
The rounding mode is one of CEILING, FLOOR, HALF_UP, HALF_DOWN,
HALF_EVEN, UP, DOWN and UNNECESSARY; it defaults to HALF_UP.
(with-redefs bindings & body)
binding => var-symbol temp-value-expr
Temporarily redefines Vars while executing the body. The
temp-value-exprs will be evaluated and each resulting value will
replace in parallel the root value of its Var. After the body is
executed, the root values of all the Vars will be set back to their
old values. These temporary changes will be visible in all threads.
Useful for mocking out functions during testing.
(with-redefs-fn binding-map func)
Temporarily redefines Vars during a call to func. Each val of
binding-map will replace the root value of its key which must be
a Var. After func is called with no args, the root values of all
the Vars will be set back to their old values. These temporary
changes will be visible in all threads. Useful for mocking out
functions during testing.