Provides a macro called 'define-match'. 'define-match' makes it possible to write pattern matcher functions which are similar to Qi and Shen.
See test.scm for examples. Here is one of the tests:
;;;;;;;; Quick sort
(define-match keep
[ ] ____ :> '[]
[A . Rest] Pred :> (cons A (keep Rest Pred)) :where (Pred A)
[_ . Rest] Pred :> (keep Rest Pred))
(define-match quicksort
[] :> '[]
[A . R] :> (append (quicksort (keep R (lambda (B) (>= A B))))
(list A)
(quicksort (keep R (lambda (B) (< A B))))))
(test (quicksort '[6 8 5 9 3 2 2 1 4 7])
'[1 2 2 3 4 5 6 7 8 9])The macro is by itself written using the 'define-match' macro, bootstrapped from shen. Here is one of the functions:
(define-match transform-to-check-similarities-0
R _ R _______ :> R
[if Test Body F] F R Varlist :> `[if ,Test ,(transform-to-check-similarities-0 Body F R Varlist) ,F]
[let [[Varname Value]] Body] F R Varlist :> (let ((Prev-value (varlist-value Varname Varlist)))
(if (eq? Prev-value '___not-in-varlist)
`[let [[,Varname ,Value]]
,(transform-to-check-similarities-0 Body F R (cons-varlist Varname Value Varlist))]
`[if [equal? ,Varname ,Value]
,(transform-to-check-similarities-0 Body F R Varlist)
,F]))
[let Vars Body] F R Varlist :> `[let ,Vars ,(transform-to-check-similarities-0 Body F R Varlist)])
Copyright 2014 SUN/OPSYS at University of Oslo.
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