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peg: helper macro docstrings

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* module/ice-9/peg.scm: Convert the helper macro comments into
  docstrings.
This commit is contained in:
Andy Wingo 2011-02-18 10:33:03 +01:00
parent 09a6a7a44a
commit 87c3ef2f95
1 changed files with 10 additions and 14 deletions
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24
module/ice-9/peg.scm
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@ -37,49 +37,45 @@
#:use-module (system base pmatch)
#:use-module (ice-9 pretty-print))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;; LOOPING CONSTRUCTS
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;
;;; Helper Macros
;;;
;; Perform ACTION. If it succeeded, return its return value. If it failed, run
;; IF_FAILS and try again
(define-syntax until
(syntax-rules ()
"Evaluate TEST. If it is true, return its value. Otherwise,
execute the STMTs and try again."
((_ test stmt stmt* ...)
(let lp ()
(or test
(begin stmt stmt* ... (lp)))))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;; GENERIC LIST-PROCESSING MACROS
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Return #t if the list has only one element (calling length all the time on
;; potentially long lists was really slow).
(define-syntax single?
(syntax-rules ()
"Return #t if X is a list of one element."
((_ x)
(pmatch x
((_) #t)
(else #f)))))
;; Push an object onto a list.
(define-syntax push!
(syntax-rules ()
"Push an object onto a list."
((_ lst obj)
(set! lst (cons obj lst)))))
;; If SYM is a list of one element, return (car SYM), else return SYM.
(define-syntax single-filter
(syntax-rules ()
"If EXP is a list of one element, return the element. Otherwise
return EXP."
((_ exp)
(pmatch exp
((,elt) elt)
(,elts elts)))))
;; If OBJ is non-null, push it onto LST, otherwise do nothing.
(define-syntax push-not-null!
(syntax-rules ()
"If OBJ is non-null, push it onto LST, otherwise do nothing."
((_ lst obj)
(if (not (null? obj))
(push! lst obj)))))