clojure.pprint
A Pretty Printer for Clojure
clojure.pprint implements a flexible system for printing structured data
in a pleasing, easy-to-understand format. Basic use of the pretty printer is
simple, just call pprint instead of println. More advanced users can use
the building blocks provided to create custom output formats.
Out of the box, pprint supports a simple structured format for basic data
and a specialized format for Clojure source code. More advanced formats,
including formats that don't look like Clojure data at all like XML and
JSON, can be rendered by creating custom dispatch functions.
In addition to the pprint function, this module contains cl-format, a text
formatting function which is fully compatible with the format function in
Common Lisp. Because pretty printing directives are directly integrated with
cl-format, it supports very concise custom dispatch. It also provides
a more powerful alternative to Clojure's standard format function.
See documentation for pprint and cl-format for more information or
complete documentation on the Clojure web site on GitHub.
*print-base*
The base to use for printing integers and rationals.
*print-miser-width*
The column at which to enter miser style. Depending on the dispatch table,
miser style add newlines in more places to try to keep lines short allowing for further
levels of nesting.
*print-pprint-dispatch*
The pretty print dispatch function. Use with-pprint-dispatch or set-pprint-dispatch
to modify.
*print-radix*
Print a radix specifier in front of integers and rationals. If *print-base* is 2, 8,
or 16, then the radix specifier used is #b, #o, or #x, respectively. Otherwise the
radix specifier is in the form #XXr where XX is the decimal value of *print-base*
*print-right-margin*
Pretty printing will try to avoid anything going beyond this column.
Set it to nil to have pprint let the line be arbitrarily long. This will ignore all
non-mandatory newlines.
*print-suppress-namespaces*
Don't print namespaces with symbols. This is particularly useful when
pretty printing the results of macro expansions
(cl-format writer format-in & args)
An implementation of a Common Lisp compatible format function. cl-format formats its
arguments to an output stream or string based on the format control string given. It
supports sophisticated formatting of structured data.
Writer is an instance of java.io.Writer, true to output to *out* or nil to output
to a string, format-in is the format control string and the remaining arguments
are the data to be formatted.
The format control string is a string to be output with embedded 'format directives'
describing how to format the various arguments passed in.
If writer is nil, cl-format returns the formatted result string. Otherwise, cl-format
returns nil.
For example:
(let [results [46 38 22]]
(cl-format true "There ~[are~;is~:;are~]~:* ~d result~:p: ~{~d~^, ~}~%"
(count results) results))
Prints to *out*:
There are 3 results: 46, 38, 22
Detailed documentation on format control strings is available in the "Common Lisp the
Language, 2nd edition", Chapter 22 (available online at:
http://www.cs.cmu.edu/afs/cs.cmu.edu/project/ai-repository/ai/html/cltl/clm/node200.html#SECTION002633000000000000000)
and in the Common Lisp HyperSpec at
http://www.lispworks.com/documentation/HyperSpec/Body/22_c.htm
(formatter format-in)
Makes a function which can directly run format-in. The function is
fn [stream & args] ... and returns nil unless the stream is nil (meaning
output to a string) in which case it returns the resulting string.
format-in can be either a control string or a previously compiled format.
(formatter-out format-in)
Makes a function which can directly run format-in. The function is
fn [& args] ... and returns nil. This version of the formatter macro is
designed to be used with *out* set to an appropriate Writer. In particular,
this is meant to be used as part of a pretty printer dispatch method.
format-in can be either a control string or a previously compiled format.
(fresh-line)
Make a newline if *out* is not already at the beginning of the line. If *out* is
not a pretty writer (which keeps track of columns), this function always outputs a newline.
(get-pretty-writer writer)
Returns the java.io.Writer passed in wrapped in a pretty writer proxy, unless it's
already a pretty writer. Generally, it is unnecessary to call this function, since pprint,
write, and cl-format all call it if they need to. However if you want the state to be
preserved across calls, you will want to wrap them with this.
For example, when you want to generate column-aware output with multiple calls to cl-format,
do it like in this example:
(defn print-table [aseq column-width]
(binding [*out* (get-pretty-writer *out*)]
(doseq [row aseq]
(doseq [col row]
(cl-format true "~4D~7,vT" col column-width))
(prn))))
Now when you run:
user> (print-table (map #(vector % (* % %) (* % % %)) (range 1 11)) 8)
It prints a table of squares and cubes for the numbers from 1 to 10:
1 1 1
2 4 8
3 9 27
4 16 64
5 25 125
6 36 216
7 49 343
8 64 512
9 81 729
10 100 1000
(pp)
A convenience macro that pretty prints the last thing output. This is
exactly equivalent to (pprint *1).
(pprint-indent relative-to n)
Create an indent at this point in the pretty printing stream. This defines how
following lines are indented. relative-to can be either :block or :current depending
whether the indent should be computed relative to the start of the logical block or
the current column position. n is an offset.
This function is intended for use when writing custom dispatch functions.
Output is sent to *out* which must be a pretty printing writer.
(pprint-logical-block options* body)
Execute the body as a pretty printing logical block with output to *out* which
must be a pretty printing writer. When used from pprint or cl-format, this can be
assumed.
This function is intended for use when writing custom dispatch functions.
Before the body, the caller can optionally specify options: :prefix, :per-line-prefix,
and :suffix.
(pprint-newline kind)
Print a conditional newline to a pretty printing stream. kind specifies if the
newline is :linear, :miser, :fill, or :mandatory.
This function is intended for use when writing custom dispatch functions.
Output is sent to *out* which must be a pretty printing writer.
(pprint-tab kind colnum colinc)
Tab at this point in the pretty printing stream. kind specifies whether the tab
is :line, :section, :line-relative, or :section-relative.
Colnum and colinc specify the target column and the increment to move the target
forward if the output is already past the original target.
This function is intended for use when writing custom dispatch functions.
Output is sent to *out* which must be a pretty printing writer.
THIS FUNCTION IS NOT YET IMPLEMENTED.
(print-table ks rows)
(print-table rows)
Prints a collection of maps in a textual table. Prints table headings
ks, and then a line of output for each row, corresponding to the keys
in ks. If ks are not specified, use the keys of the first item in rows.
(set-pprint-dispatch function)
Set the pretty print dispatch function to a function matching (fn [obj] ...)
where obj is the object to pretty print. That function will be called with *out* set
to a pretty printing writer to which it should do its printing.
For example functions, see simple-dispatch and code-dispatch in
clojure.pprint.dispatch.clj.
(write object & kw-args)
Write an object subject to the current bindings of the printer control variables.
Use the kw-args argument to override individual variables for this call (and any
recursive calls). Returns the string result if :stream is nil or nil otherwise.
The following keyword arguments can be passed with values:
Keyword Meaning Default value
:stream Writer for output or nil true (indicates *out*)
:base Base to use for writing rationals Current value of *print-base*
:circle* If true, mark circular structures Current value of *print-circle*
:length Maximum elements to show in sublists Current value of *print-length*
:level Maximum depth Current value of *print-level*
:lines* Maximum lines of output Current value of *print-lines*
:miser-width Width to enter miser mode Current value of *print-miser-width*
:dispatch The pretty print dispatch function Current value of *print-pprint-dispatch*
:pretty If true, do pretty printing Current value of *print-pretty*
:radix If true, prepend a radix specifier Current value of *print-radix*
:readably* If true, print readably Current value of *print-readably*
:right-margin The column for the right margin Current value of *print-right-margin*
:suppress-namespaces If true, no namespaces in symbols Current value of *print-suppress-namespaces*
* = not yet supported
(write-out object)
Write an object to *out* subject to the current bindings of the printer control
variables. Use the kw-args argument to override individual variables for this call (and
any recursive calls).
*out* must be a PrettyWriter if pretty printing is enabled. This is the responsibility
of the caller.
This method is primarily intended for use by pretty print dispatch functions that
already know that the pretty printer will have set up their environment appropriately.
Normal library clients should use the standard "write" interface.