racket/collects/honu/utils.ss
Stevie Strickland 7dbb99d3c6 merged 292:296 from branches/sstrickl
svn: r297
2005-07-02 04:03:02 +00:00

60 lines
1.6 KiB
Scheme

(module utils mzscheme
(require "ast.ss")
(require (lib "list.ss" "srfi" "1"))
(provide fold-with-rest)
(define (fold-with-rest f init l)
(if (null? l)
init
(fold-with-rest f (f (car l) (cdr l) init) (cdr l))))
(provide unique?)
(define (unique? cs)
(fold-with-rest (lambda (c cs acc)
(and acc
(not (member c cs))))
#t cs))
(define (get-names ds p f)
(filter-map (lambda (defn)
(and (p defn)
(f defn)))
ds))
(provide map-and-fold)
(define (map-and-fold f i l)
(let loop ((l l)
(mapped '())
(folded i))
(if (null? l)
(values (reverse mapped) folded)
(let-values ([(res folded) (f (car l) folded)])
(loop (cdr l)
(cons res mapped)
folded)))))
(provide map-two-values)
(define (map-two-values f . lists)
(let loop ((lists lists)
(map1 '())
(map2 '()))
(if (any null? lists)
(values (reverse map1) (reverse map2))
(let-values ([(m1 m2) (apply f (map car lists))])
(loop (map cdr lists)
(cons m1 map1)
(cons m2 map2))))))
(provide partition-first)
(define (partition-first f lis)
(let loop ([lis lis]
[passed '()])
(cond
[(null? lis)
(values #f (reverse passed))]
[(f (car lis))
(values (car lis) (append (reverse passed) (cdr lis)))]
[else
(loop (cdr lis) (cons (car lis) passed))])))
)