[[tags: egg]]
[[toc:]]
== chalk
Simple hahn-style in-source documentation
=== Introduction
Chalk attempts to be a simpler alternative to Chicken 4's
[[https://wiki.call-cc.org/eggref/4/hahn|hahn]] +
[[https://wiki.call-cc.org/eggref/4/hahn-utils|hahn-utils]], generating wiki
output with support for procedure, variables, syntax, modules, include files,
and egg files. It tries to be as basic as possible, performing almost no code
analysis and no evaluation, while making it easy to generate documentation from
one or more files.
The following is hahn's fibonacci example, rewritten for chalk. Note key
differences: The example is simply a string (and therefore not evaluated),
whith the option of a {{@pre}} or {{@post}} caption. Additionally, the
docstring must be contained within a single string and a heading is not
generated for the procedure name.
(define (fibonacci n)
@("Computes the nth [[http://en.wikipedia.org/wiki/Fibonacci_number|Fibonacci]].
This naïve algorithm runs in ''O(2^n)''; using e.g. memoization, we could bring
it down to ''O(n)''."
(n "The nth number to calculate")
(@to "integer")
(@example
(@pre "For example, computing the 6th Fibonnaci number (starting from 0)")
"(fibonacci 6) ; => 8"))
(case n
((0) 0)
((1) 1)
(else (+ (fibonacci (- n 1))
(fibonacci (- n 2))))))
Which produces the following wiki output:
(fibonacci n) → integer
Computes the nth [[http://en.wikipedia.org/wiki/Fibonacci_number|Fibonacci]].
This naïve algorithm runs in ''O(2^n)''; using e.g. memoization, we could bring
it down to ''O(n)''.
; n : The nth number to calculate
For example, computing the 6th Fibonnaci number (starting from 0)
(fibonacci 6) ; => 8
=== Syntax
Most expressions of the following form can be documented to varying degrees of
automation, where {{SIGNATURE}} can be a pair (as in a procedure definition).
(DEFINE SIGNATURE BODY ...)
Documentation entails inserting a docexpr of the following form before the
{{BODY}}.
@("Description" [OPTION] ...)
==== Variables
Variables are documented as follows, ignoring potentially disastrous rounding practices:
(define pi @("The ratio of a circle's circumference to its diameter.") 3.14)
The special tag {{@internal}} can be used to suppress output, and is useful for
documenting unexported variables internally:
(define counter
@("How many times thing has happened."
(@internal)))
==== Procedures
Procedures are documented similarly, but can contain the tags, {{@to}}, and
{{@example}}, as well as listing function parameters:
(define (foobar a b)
@("Does baz."
(a "An input")
(b "Another input")
(@to integer)
(@example
(@pre "For example, to do baz with foobar:")
"(foobar blarg arg) ; => 4"))
(baz))
In the case of procedures defined as variables, chalk considers it a variable
by default, using the function name as a signature. In either case, you can
override the default signature with the tag {{@sig}}, and you can specify that
it is indeed a procedure as follows:
(define function?
@(fn "This is definitely a function"
(@sig (function? a b c)))
(lambda () (print "bar")))
You can specify that a variable definition is a procedure with any of {{fn}},
{{proc}}, {{function}}, or {{procedure}} in the first position of the docexpr.
Tags behave as follows:
; @to : A string or expression to be inserted as {{→ expr}}
; @example : A string to be enscripted with scheme highlighting, with optional {{@pre}} or {{@post}} caption.
; @sig : A string or expression that override the procedure signature
; @internal : Suppress output, documented for internal use.
==== Syntax definitions
Syntax definitions accept the same tags and is defined equivalently to
procedures, provided that it is is defined using {{define-syntax}}. The
{{@sig}} tag is especially useful for specifying syntax usage, since chalk
won't automatically detect the signature. Here's a rather silly example:
(define-syntax hello
@("Hello there!"
(@sig (hello a b c)))
(syntax-rules ()
((_ a b c)
"Hello there!")))
For syntax defined otherwise, you can specify that it is syntax like so:
(define-syntax-rule (hello a b c)
@(syntax "Hello")
"Hello there")
You can specify that a definition is syntax with either {{syntax}} or {{macro}}
in the first position of the docexpr.
==== Records
Currently, two types of record definitions are supported - {{define-record}}
and {{define-record-type}} from {{chicken.base}}. Records can be documented
internally by specifying a {{@internal}} file, and they accept one more tag
{{@full}}. When specified, it generates a list of all of the procedures
associated with that record definition. Otherwise, only the record name is
documented, and procedure documentation can be added manually.
For example:
(define-record point
@("A point"
(@full))
x y)
Produces the following output:
point
(make-point x y)
point?
point-x
point-y
A point
==== Top-level documentation
A docexpr outside of a definition can be used to insert arbitrary text.
Additionally, the following top-level tags are supported:
; script : Generate an enscript segment, with optional highlight tag. Can contain multiple strings.
@(script
(@highlight "scheme")
"(print \"hello\")"
"(print 4)")
In addition to the {{@highlight}} tag, a caption can be inserted before or
after a script using the tags {{@pre}} and {{@post}}.
; heading, title, == : A title
@(== "My egg")
Various subheadings:
; subheading, subtitle, === :
; subsubheading, subsubtitle, ==== :
; subsubsubsubheading, subsubsubsubtitle, ===== :
; deflist : A definition list such as this one
@(deflist
(key "value")
(definitionless-term)
(term "definition"))
Lists and tables are not currently supported, but are planned for the future.
In the meantime, unsupported forms of wiki syntax can be inserted literally
using a top-level docexpr.
=== Compiling and running programs
To compile a scheme file containing chalk special syntax, you can use {{-X
chalk}}. For script usage (e.g. with {{csi -s}}), you can use {{import chalk}}.
=== Chalk program usage
The chalk program generates output to stdout or a specified output file based
on the given input file(s), and optionally: a {{.egg}} file, a
{{.release-info}} file, and/or a {{LICENSE}} file. For more info, see {{chalk --help}}:
Usage: chalk [OPTION]... [FILE]...
-h, --help Print usage
-o, --output=FILE Write to file
-i, --ignore-egg Ignore .egg file
-r, --ignore-release Ignore .release-info file
-n, --no-toc Don't add a toc
-e, --email=EMAIL Include EMAIL with author
-H, --head=FILE File to add to beginning of documentation
-P, --prologue=FILE File to add after synopsis
-E, --epilogue=FILE File to add before maintainer info
-T, --tail=FILE File to add to end of documentation
-L, --license[=FILE] Whether to insert a license
-m, --module-headers Create === Module-name headers
A {{.release-info}} file can contain optional comments following {{release}}
expressions (on the same line), which are used as version descriptions when
generating a version history section of the documentation, for example:
(uri targz "https://example-url.com")
(release "0.3.1") ; Fixes bug
(release "0.3.0") ; Adds feature
(release "0.2.0")
(release "0.1.0") ; Initial version
=== Full Example
Coming soon
=== Author
Diego A. Mundo
=== Version History
; 0.3.2 : Add multi-line script support
; 0.3.1 : Fix bug: release-info not ignored on ignore-egg
; 0.3.0 : Add support for records and syntax
; 0.2.0 : Add @example, listed function parameters, script caption
; 0.1.0 : Initial version