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;;; data-structures.scm - Optional data structures extensions
;
; Copyright (c) 2008-2016, The CHICKEN Team
; All rights reserved.
;
; Redistribution and use in source and binary forms, with or without
; modification, are permitted provided that the following conditions
; are met:
;
; Redistributions of source code must retain the above copyright notice, this list of conditions and the following
; disclaimer.
; Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
; disclaimer in the documentation and/or other materials provided with the distribution.
; Neither the name of the author nor the names of its contributors may be used to endorse or promote
; products derived from this software without specific prior written permission.
;
; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS
; OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
; AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
; CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
; CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
; SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
; OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
; POSSIBILITY OF SUCH DAMAGE.
(declare
(unit data-structures))
(include "common-declarations.scm")
(register-feature! 'data-structures)
;;; Combinators:
(define (identity x) x)
(define (conjoin . preds)
(lambda (x)
(let loop ([preds preds])
(or (null? preds)
(and ((##sys#slot preds 0) x)
(loop (##sys#slot preds 1)) ) ) ) ) )
(define (disjoin . preds)
(lambda (x)
(let loop ([preds preds])
(and (not (null? preds))
(or ((##sys#slot preds 0) x)
(loop (##sys#slot preds 1)) ) ) ) ) )
(define (constantly . xs)
(if (eq? 1 (length xs))
(let ([x (car xs)])
(lambda _ x) )
(lambda _ (apply values xs)) ) )
(define (flip proc) (lambda (x y) (proc y x)))
(define complement
(lambda (p)
(lambda args (not (apply p args))) ) )
(define (compose . fns)
(define (rec f0 . fns)
(if (null? fns)
f0
(lambda args
(call-with-values
(lambda () (apply (apply rec fns) args))
f0) ) ) )
(if (null? fns)
values
(apply rec fns) ) )
(define (o . fns)
(if (null? fns)
identity
(let loop ((fns fns))
(let ((h (##sys#slot fns 0))
(t (##sys#slot fns 1)) )
(if (null? t)
h
(lambda (x) (h ((loop t) x))))))))
(define (list-of? pred)
(lambda (lst)
(let loop ([lst lst])
(cond [(null? lst) #t]
[(not-pair? lst) #f]
[(pred (##sys#slot lst 0)) (loop (##sys#slot lst 1))]
[else #f] ) ) ) )
(define (each . procs)
(cond ((null? procs) (lambda _ (void)))
((null? (##sys#slot procs 1)) (##sys#slot procs 0))
(else
(lambda args
(let loop ((procs procs))
(let ((h (##sys#slot procs 0))
(t (##sys#slot procs 1)) )
(if (null? t)
(apply h args)
(begin
(apply h args)
(loop t) ) ) ) ) ) ) ) )
(define (any? x) #t)
;;; List operators:
(define (atom? x) (##core#inline "C_i_not_pair_p" x))
(define (tail? x y)
(##sys#check-list y 'tail?)
(or (##core#inline "C_eqp" x '())
(let loop ((y y))
(cond ((##core#inline "C_eqp" y '()) #f)
((##core#inline "C_eqp" x y) #t)
(else (loop (##sys#slot y 1))) ) ) ) )
(define intersperse
(lambda (lst x)
(let loop ((ns lst))
(if (##core#inline "C_eqp" ns '())
ns
(let ((tail (cdr ns)))
(if (##core#inline "C_eqp" tail '())
ns
(cons (##sys#slot ns 0) (cons x (loop tail))) ) ) ) ) ) )
(define (butlast lst)
(##sys#check-pair lst 'butlast)
(let loop ((lst lst))
(let ((next (##sys#slot lst 1)))
(if (and (##core#inline "C_blockp" next) (##core#inline "C_pairp" next))
(cons (##sys#slot lst 0) (loop next))
'() ) ) ) )
(define (flatten . lists0)
(let loop ([lists lists0] [rest '()])
(cond [(null? lists) rest]
[else
(let ([head (##sys#slot lists 0)]
[tail (##sys#slot lists 1)] )
(if (list? head)
(loop head (loop tail rest))
(cons head (loop tail rest)) ) ) ] ) ) )
(define chop
(lambda (lst n)
(##sys#check-exact n 'chop)
(when (fx<= n 0) (##sys#error 'chop "invalid numeric argument" n))
(let ([len (length lst)])
(let loop ([lst lst] [i len])
(cond [(null? lst) '()]
[(fx< i n) (list lst)]
[else
(do ([hd '() (cons (##sys#slot tl 0) hd)]
[tl lst (##sys#slot tl 1)]
[c n (fx- c 1)] )
((fx= c 0)
(cons (reverse hd) (loop tl (fx- i n))) ) ) ] ) ) ) ) )
(define (join lsts . lst)
(let ([lst (if (pair? lst) (car lst) '())])
(##sys#check-list lst 'join)
(let loop ([lsts lsts])
(cond [(null? lsts) '()]
[(not (pair? lsts))
(##sys#error-not-a-proper-list lsts) ]
[else
(let ([l (##sys#slot lsts 0)]
[r (##sys#slot lsts 1)] )
(if (null? r)
l
(##sys#append l lst (loop r)) ) ) ] ) ) ) )
(define compress
(lambda (blst lst)
(let ([msg "bad argument type - not a proper list"])
(##sys#check-list lst 'compress)
(let loop ([blst blst] [lst lst])
(cond [(null? blst) '()]
[(not (pair? blst))
(##sys#signal-hook #:type-error 'compress msg blst) ]
[(not (pair? lst))
(##sys#signal-hook #:type-error 'compress msg lst) ]
[(##sys#slot blst 0)
(cons (##sys#slot lst 0) (loop (##sys#slot blst 1) (##sys#slot lst 1)))]
[else (loop (##sys#slot blst 1) (##sys#slot lst 1))] ) ) ) ) )
;;; Alists:
(define (alist-update! x y lst #!optional (cmp eqv?))
(let* ([aq (cond [(eq? eq? cmp) assq]
[(eq? eqv? cmp) assv]
[(eq? equal? cmp) assoc]
[else
(lambda (x lst)
(let loop ([lst lst])
(and (pair? lst)
(let ([a (##sys#slot lst 0)])
(if (and (pair? a) (cmp x (##sys#slot a 0)))
a
(loop (##sys#slot lst 1)) ) ) ) ) ) ] ) ]
[item (aq x lst)] )
(if item
(begin
(##sys#setslot item 1 y)
lst)
(cons (cons x y) lst) ) ) )
(define (alist-update k v lst #!optional (cmp eqv?))
(let loop ((lst lst))
(cond ((null? lst)
(list (cons k v)))
((not (pair? lst))
(error 'alist-update "bad argument type" lst))
(else
(let ((a (##sys#slot lst 0)))
(cond ((not (pair? a))
(error 'alist-update "bad argument type" a))
((cmp k (##sys#slot a 0))
(cons (cons k v) (##sys#slot lst 1)))
(else
(cons (cons (##sys#slot a 0) (##sys#slot a 1))
(loop (##sys#slot lst 1))))))))))
(define (alist-ref x lst #!optional (cmp eqv?) (default #f))
(let* ((aq (cond ((eq? eq? cmp) assq)
((eq? eqv? cmp) assv)
((eq? equal? cmp) assoc)
(else
(lambda (x lst)
(let loop ((lst lst))
(cond
((null? lst) #f)
((pair? lst)
(let ((a (##sys#slot lst 0)))
(##sys#check-pair a 'alist-ref)
(if (cmp x (##sys#slot a 0))
a
(loop (##sys#slot lst 1)) ) ))
(else (error 'alist-ref "bad argument type" lst)) ) ) ) ) ) )
(item (aq x lst)) )
(if item
(##sys#slot item 1)
default) ) )
(define (rassoc x lst . tst)
(##sys#check-list lst 'rassoc)
(let ([tst (if (pair? tst) (car tst) eqv?)])
(let loop ([l lst])
(and (pair? l)
(let ([a (##sys#slot l 0)])
(##sys#check-pair a 'rassoc)
(if (tst x (##sys#slot a 1))
a
(loop (##sys#slot l 1)) ) ) ) ) ) )
; (reverse-string-append l) = (apply string-append (reverse l))
(define (reverse-string-append l)
(define (rev-string-append l i)
(if (pair? l)
(let* ((str (car l))
(len (string-length str))
(result (rev-string-append (cdr l) (fx+ i len))))
(let loop ((j 0) (k (fx- (fx- (string-length result) i) len)))
(if (fx< j len)
(begin
(string-set! result k (string-ref str j))
(loop (fx+ j 1) (fx+ k 1)))
result)))
(make-string i)))
(rev-string-append l 0))
;;; Anything->string conversion:
(define ->string
(lambda (x)
(cond [(string? x) x]
[(symbol? x) (symbol->string x)]
[(char? x) (string x)]
[(number? x) (##sys#number->string x)]
[else
(let ([o (open-output-string)])
(display x o)
(get-output-string o) ) ] ) ) )
(define conc
(lambda args
(apply string-append (map ->string args)) ) )
;;; Search one string inside another:
(let ()
(define (traverse which where start test loc)
(##sys#check-string which loc)
(##sys#check-string where loc)
(let* ((wherelen (##sys#size where))
(whichlen (##sys#size which))
(end (fx- wherelen whichlen)))
(##sys#check-exact start loc)
(if (and (fx>= start 0)
(fx>= wherelen start))
(if (fx= whichlen 0)
start
(and (fx>= end 0)
(let loop ((istart start))
(cond ((fx> istart end) #f)
((test istart whichlen) istart)
(else (loop (fx+ istart 1)))))))
(##sys#error-hook (foreign-value "C_OUT_OF_RANGE_ERROR" int)
loc
start
wherelen))))
(set! ##sys#substring-index
(lambda (which where start)
(traverse
which where start
(lambda (i l) (##core#inline "C_substring_compare" which where 0 i l))
'substring-index) ) )
(set! ##sys#substring-index-ci
(lambda (which where start)
(traverse
which where start
(lambda (i l) (##core#inline "C_substring_compare_case_insensitive" which where 0 i l))
'substring-index-ci) ) ) )
(define (substring-index which where #!optional (start 0))
(##sys#substring-index which where start) )
(define (substring-index-ci which where #!optional (start 0))
(##sys#substring-index-ci which where start) )
;;; 3-Way string comparison:
(define (string-compare3 s1 s2)
(##sys#check-string s1 'string-compare3)
(##sys#check-string s2 'string-compare3)
(let ((len1 (##sys#size s1))
(len2 (##sys#size s2)) )
(let* ((len-diff (fx- len1 len2))
(cmp (##core#inline "C_string_compare" s1 s2 (if (fx< len-diff 0) len1 len2))))
(if (fx= cmp 0)
len-diff
cmp))))
(define (string-compare3-ci s1 s2)
(##sys#check-string s1 'string-compare3-ci)
(##sys#check-string s2 'string-compare3-ci)
(let ((len1 (##sys#size s1))
(len2 (##sys#size s2)) )
(let* ((len-diff (fx- len1 len2))
(cmp (##core#inline "C_string_compare_case_insensitive" s1 s2 (if (fx< len-diff 0) len1 len2))))
(if (fx= cmp 0)
len-diff
cmp))))
;;; Substring comparison:
(define (##sys#substring=? s1 s2 start1 start2 n)
(##sys#check-string s1 'substring=?)
(##sys#check-string s2 'substring=?)
(let ((len (or n
(fxmin (fx- (##sys#size s1) start1)
(fx- (##sys#size s2) start2) ) ) ) )
(##sys#check-exact start1 'substring=?)
(##sys#check-exact start2 'substring=?)
(##core#inline "C_substring_compare" s1 s2 start1 start2 len) ) )
(define (substring=? s1 s2 #!optional (start1 0) (start2 0) len)
(##sys#substring=? s1 s2 start1 start2 len) )
(define (##sys#substring-ci=? s1 s2 start1 start2 n)
(##sys#check-string s1 'substring-ci=?)
(##sys#check-string s2 'substring-ci=?)
(let ((len (or n
(fxmin (fx- (##sys#size s1) start1)
(fx- (##sys#size s2) start2) ) ) ) )
(##sys#check-exact start1 'substring-ci=?)
(##sys#check-exact start2 'substring-ci=?)
(##core#inline "C_substring_compare_case_insensitive"
s1 s2 start1 start2 len) ) )
(define (substring-ci=? s1 s2 #!optional (start1 0) (start2 0) len)
(##sys#substring-ci=? s1 s2 start1 start2 len) )
;;; Split string into substrings:
(define string-split
(lambda (str . delstr-and-flag)
(##sys#check-string str 'string-split)
(let* ([del (if (null? delstr-and-flag) "\t\n " (car delstr-and-flag))]
[flag (if (fx= (length delstr-and-flag) 2) (cadr delstr-and-flag) #f)]
[strlen (##sys#size str)] )
(##sys#check-string del 'string-split)
(let ([dellen (##sys#size del)]
[first #f] )
(define (add from to last)
(let ([node (cons (##sys#substring str from to) '())])
(if first
(##sys#setslot last 1 node)
(set! first node) )
node) )
(let loop ([i 0] [last #f] [from 0])
(cond [(fx>= i strlen)
(when (or (fx> i from) flag) (add from i last))
(or first '()) ]
[else
(let ([c (##core#inline "C_subchar" str i)])
(let scan ([j 0])
(cond [(fx>= j dellen) (loop (fx+ i 1) last from)]
[(eq? c (##core#inline "C_subchar" del j))
(let ([i2 (fx+ i 1)])
(if (or (fx> i from) flag)
(loop i2 (add from i last) i2)
(loop i2 last i2) ) ) ]
[else (scan (fx+ j 1))] ) ) ) ] ) ) ) ) ) )
;;; Concatenate list of strings:
(define (string-intersperse strs #!optional (ds " "))
(##sys#check-list strs 'string-intersperse)
(##sys#check-string ds 'string-intersperse)
(let ((dslen (##sys#size ds)))
(let loop1 ((ss strs) (n 0))
(cond ((##core#inline "C_eqp" ss '())
(if (##core#inline "C_eqp" strs '())
""
(let ((str2 (##sys#allocate-vector (fx- n dslen) #t #\space #f)))
(let loop2 ((ss2 strs) (n2 0))
(let* ((stri (##sys#slot ss2 0))
(next (##sys#slot ss2 1))
(strilen (##sys#size stri)) )
(##core#inline "C_substring_copy" stri str2 0 strilen n2)
(let ((n3 (fx+ n2 strilen)))
(if (##core#inline "C_eqp" next '())
str2
(begin
(##core#inline "C_substring_copy" ds str2 0 dslen n3)
(loop2 next (fx+ n3 dslen)) ) ) ) ) ) ) ) )
((and (##core#inline "C_blockp" ss) (##core#inline "C_pairp" ss))
(let ((stri (##sys#slot ss 0)))
(##sys#check-string stri 'string-intersperse)
(loop1 (##sys#slot ss 1)
(fx+ (##sys#size stri) (fx+ dslen n)) ) ) )
(else (##sys#error-not-a-proper-list strs)) ) ) ) )
;;; Translate elements of a string:
(define string-translate
(lambda (str from . to)
(define (instring s)
(let ([len (##sys#size s)])
(lambda (c)
(let loop ([i 0])
(cond [(fx>= i len) #f]
[(eq? c (##core#inline "C_subchar" s i)) i]
[else (loop (fx+ i 1))] ) ) ) ) )
(let* ([from
(cond [(char? from) (lambda (c) (eq? c from))]
[(pair? from) (instring (list->string from))]
[else
(##sys#check-string from 'string-translate)
(instring from) ] ) ]
[to
(and (pair? to)
(let ([tx (##sys#slot to 0)])
(cond [(char? tx) tx]
[(pair? tx) (list->string tx)]
[else
(##sys#check-string tx 'string-translate)
tx] ) ) ) ]
[tlen (and (string? to) (##sys#size to))] )
(##sys#check-string str 'string-translate)
(let* ([slen (##sys#size str)]
[str2 (make-string slen)] )
(let loop ([i 0] [j 0])
(if (fx>= i slen)
(if (fx< j i)
(##sys#substring str2 0 j)
str2)
(let* ([ci (##core#inline "C_subchar" str i)]
[found (from ci)] )
(cond [(not found)
(##core#inline "C_setsubchar" str2 j ci)
(loop (fx+ i 1) (fx+ j 1)) ]
[(not to) (loop (fx+ i 1) j)]
[(char? to)
(##core#inline "C_setsubchar" str2 j to)
(loop (fx+ i 1) (fx+ j 1)) ]
[(fx>= found tlen)
(##sys#error 'string-translate "invalid translation destination" i to) ]
[else
(##core#inline "C_setsubchar" str2 j (##core#inline "C_subchar" to found))
(loop (fx+ i 1) (fx+ j 1)) ] ) ) ) ) ) ) ) )
(define (string-translate* str smap)
(##sys#check-string str 'string-translate*)
(##sys#check-list smap 'string-translate*)
(let ((len (##sys#size str)))
(define (collect i from total fs)
(if (fx>= i len)
(##sys#fragments->string
total
(##sys#fast-reverse
(if (fx> i from)
(cons (##sys#substring str from i) fs)
fs) ) )
(let loop ((smap smap))
(if (null? smap)
(collect (fx+ i 1) from (fx+ total 1) fs)
(let* ((p (car smap))
(sm (car p))
(smlen (string-length sm))
(st (cdr p)) )
(if (and (fx<= (fx+ i smlen) len)
(##core#inline "C_substring_compare" str sm i 0 smlen))
(let ((i2 (fx+ i smlen)))
(when (fx> i from)
(set! fs (cons (##sys#substring str from i) fs)) )
(collect
i2 i2
(fx+ total (string-length st))
(cons st fs) ) )
(loop (cdr smap)) ) ) ) ) ) )
(collect 0 0 0 '()) ) )
;;; Chop string into substrings:
(define (string-chop str len)
(##sys#check-string str 'string-chop)
(##sys#check-exact len 'string-chop)
(let ([total (##sys#size str)])
(let loop ([total total] [pos 0])
(cond [(fx<= total 0) '()]
[(fx<= total len) (list (##sys#substring str pos (fx+ pos total)))]
[else (cons (##sys#substring str pos (fx+ pos len)) (loop (fx- total len) (fx+ pos len)))] ) ) ) )
;;; Remove suffix
(define (string-chomp str #!optional (suffix "\n"))
(##sys#check-string str 'string-chomp)
(##sys#check-string suffix 'string-chomp)
(let* ((len (##sys#size str))
(slen (##sys#size suffix))
(diff (fx- len slen)) )
(if (and (fx>= len slen)
(##core#inline "C_substring_compare" str suffix diff 0 slen) )
(##sys#substring str 0 diff)
str) ) )
;;; Defines: sorted?, merge, merge!, sort, sort!
;;; Author : Richard A. O'Keefe (based on Prolog code by D.H.D.Warren)
;;;
;;; This code is in the public domain.
;;; Updated: 11 June 1991
;;; Modified for scheme library: Aubrey Jaffer 19 Sept. 1991
;;; Updated: 19 June 1995
;;; (sorted? sequence less?)
;;; is true when sequence is a list (x0 x1 ... xm) or a vector #(x0 ... xm)
;;; such that for all 1 <= i <= m,
;;; (not (less? (list-ref list i) (list-ref list (- i 1)))).
; Modified by flw for use with CHICKEN:
;
(define (sorted? seq less?)
(cond
((null? seq)
#t)
((vector? seq)
(let ((n (vector-length seq)))
(if (<= n 1)
#t
(do ((i 1 (+ i 1)))
((or (= i n)
(less? (vector-ref seq i)
(vector-ref seq (- i 1))))
(= i n)) )) ))
(else
(let loop ((last (car seq)) (next (cdr seq)))
(or (null? next)
(and (not (less? (car next) last))
(loop (car next) (cdr next)) )) )) ))
;;; (merge a b less?)
;;; takes two lists a and b such that (sorted? a less?) and (sorted? b less?)
;;; and returns a new list in which the elements of a and b have been stably
;;; interleaved so that (sorted? (merge a b less?) less?).
;;; Note: this does _not_ accept vectors. See below.
(define (merge a b less?)
(cond
((null? a) b)
((null? b) a)
(else (let loop ((x (car a)) (a (cdr a)) (y (car b)) (b (cdr b)))
;; The loop handles the merging of non-empty lists. It has
;; been written this way to save testing and car/cdring.
(if (less? y x)
(if (null? b)
(cons y (cons x a))
(cons y (loop x a (car b) (cdr b)) ))
;; x <= y
(if (null? a)
(cons x (cons y b))
(cons x (loop (car a) (cdr a) y b)) )) )) ))
;;; (merge! a b less?)
;;; takes two sorted lists a and b and smashes their cdr fields to form a
;;; single sorted list including the elements of both.
;;; Note: this does _not_ accept vectors.
(define (merge! a b less?)
(define (loop r a b)
(if (less? (car b) (car a))
(begin
(set-cdr! r b)
(if (null? (cdr b))
(set-cdr! b a)
(loop b a (cdr b)) ))
;; (car a) <= (car b)
(begin
(set-cdr! r a)
(if (null? (cdr a))
(set-cdr! a b)
(loop a (cdr a) b)) )) )
(cond
((null? a) b)
((null? b) a)
((less? (car b) (car a))
(if (null? (cdr b))
(set-cdr! b a)
(loop b a (cdr b)))
b)
(else ; (car a) <= (car b)
(if (null? (cdr a))
(set-cdr! a b)
(loop a (cdr a) b))
a)))
;;; (sort! sequence less?)
;;; sorts the list or vector sequence destructively. It uses a version
;;; of merge-sort invented, to the best of my knowledge, by David H. D.
;;; Warren, and first used in the DEC-10 Prolog system. R. A. O'Keefe
;;; adapted it to work destructively in Scheme.
(define (sort! seq less?)
(define (step n)
(cond
((> n 2)
(let* ((j (quotient n 2))
(a (step j))
(k (- n j))
(b (step k)))
(merge! a b less?)))
((= n 2)
(let ((x (car seq))
(y (cadr seq))
(p seq))
(set! seq (cddr seq))
(if (less? y x) (begin
(set-car! p y)
(set-car! (cdr p) x)))
(set-cdr! (cdr p) '())
p))
((= n 1)
(let ((p seq))
(set! seq (cdr seq))
(set-cdr! p '())
p))
(else
'()) ))
(if (vector? seq)
(let ((n (vector-length seq))
(vec seq))
(set! seq (vector->list seq))
(do ((p (step n) (cdr p))
(i 0 (+ i 1)))
((null? p) vec)
(vector-set! vec i (car p)) ))
;; otherwise, assume it is a list
(step (length seq)) ))
;;; (sort sequence less?)
;;; sorts a vector or list non-destructively. It does this by sorting a
;;; copy of the sequence. My understanding is that the Standard says
;;; that the result of append is always "newly allocated" except for
;;; sharing structure with "the last argument", so (append x '()) ought
;;; to be a standard way of copying a list x.
(define (sort seq less?)
(if (vector? seq)
(list->vector (sort! (vector->list seq) less?))
(sort! (append seq '()) less?)))
;;; Topological sort with cycle detection:
;;
;; A functional implementation of the algorithm described in Cormen,
;; et al. (2009), Introduction to Algorithms (3rd ed.), pp. 612-615.
(define (topological-sort dag pred)
(define (visit dag node edges path state)
(case (alist-ref node (car state) pred)
((grey)
(##sys#abort
(##sys#make-structure
'condition
'(exn runtime cycle)
`((exn . message) "cycle detected"
(exn . arguments) ,(list (cons node (reverse path)))
(exn . call-chain) ,(##sys#get-call-chain)
(exn . location) topological-sort))))
((black)
state)
(else
(let walk ((edges (or edges (alist-ref node dag pred '())))
(state (cons (cons (cons node 'grey) (car state))
(cdr state))))
(if (null? edges)
(cons (alist-update! node 'black (car state) pred)
(cons node (cdr state)))
(let ((edge (car edges)))
(walk (cdr edges)
(visit dag
edge
#f
(cons edge path)
state))))))))
(let loop ((dag dag)
(state (cons (list) (list))))
(if (null? dag)
(cdr state)
(loop (cdr dag)
(visit dag
(caar dag)
(cdar dag)
'()
state)))))
;;; Binary search:
(define binary-search
(lambda (vec proc)
(if (pair? vec)
(set! vec (list->vector vec))
(##sys#check-vector vec 'binary-search) )
(let ([len (##sys#size vec)])
(and (fx> len 0)
(let loop ([ps 0]
[pe len] )
(let ([p (fx+ ps (##core#inline "C_fixnum_shift_right" (fx- pe ps) 1))])
(let* ([x (##sys#slot vec p)]
[r (proc x)] )
(cond [(fx= r 0) p]
[(fx< r 0) (and (not (fx= pe p)) (loop ps p))]
[else (and (not (fx= ps p)) (loop p pe))] ) ) ) ) ) ) ) )
; Support for queues
;
; Written by Andrew Wilcox (awilcox@astro.psu.edu) on April 1, 1992.
;
; This code is in the public domain.
;
; (heavily adapated for use with CHICKEN by felix)
;
; Elements in a queue are stored in a list. The last pair in the list
; is stored in the queue type so that datums can be added in constant
; time.
(define (make-queue) (##sys#make-structure 'queue '() '() 0))
(define (queue? x) (##sys#structure? x 'queue))
(define (queue-length q) ; thread-safe
(##sys#check-structure q 'queue 'queue-length)
(##sys#slot q 3))
(define (queue-empty? q) ; thread-safe
(##sys#check-structure q 'queue 'queue-empty?)
(eq? '() (##sys#slot q 1)) )
(define queue-first ; thread-safe
(lambda (q)
(##sys#check-structure q 'queue 'queue-first)
(let ((first-pair (##sys#slot q 1)))
(when (eq? '() first-pair)
(##sys#error 'queue-first "queue is empty" q))
(##sys#slot first-pair 0) ) ) )
(define queue-last ; thread-safe
(lambda (q)
(##sys#check-structure q 'queue 'queue-last)
(let ((last-pair (##sys#slot q 2)))
(when (eq? '() last-pair)
(##sys#error 'queue-last "queue is empty" q))
(##sys#slot last-pair 0) ) ) )
(define (queue-add! q datum) ; thread-safe
(##sys#check-structure q 'queue 'queue-add!)
(let ((new-pair (cons datum '())))
(cond ((eq? '() (##sys#slot q 1)) (##sys#setslot q 1 new-pair))
(else (##sys#setslot (##sys#slot q 2) 1 new-pair)) )
(##sys#setslot q 2 new-pair)
(##sys#setislot q 3 (fx+ (##sys#slot q 3) 1))
(##core#undefined) ) )
(define queue-remove! ; thread-safe
(lambda (q)
(##sys#check-structure q 'queue 'queue-remove!)
(let ((first-pair (##sys#slot q 1)))
(when (eq? '() first-pair)
(##sys#error 'queue-remove! "queue is empty" q) )
(let ((first-cdr (##sys#slot first-pair 1)))
(##sys#setslot q 1 first-cdr)
(if (eq? '() first-cdr)
(##sys#setslot q 2 '()) )
(##sys#setislot q 3 (fx- (##sys#slot q 3) 1))
(##sys#slot first-pair 0) ) ) ) )
(define (queue->list q)
(##sys#check-structure q 'queue 'queue->list)
(let loop ((lst (##sys#slot q 1)) (lst2 '()))
(if (null? lst)
(##sys#fast-reverse lst2)
(loop (##sys#slot lst 1) (cons (##sys#slot lst 0) lst2)))))
(define (list->queue lst0)
(##sys#check-list lst0 'list->queue)
(##sys#make-structure
'queue lst0
(if (eq? lst0 '())
'()
(do ((lst lst0 (##sys#slot lst 1)))
((eq? (##sys#slot lst 1) '()) lst)
(if (or (not (##core#inline "C_blockp" lst))
(not (##core#inline "C_pairp" lst)) )
(##sys#error-not-a-proper-list lst0 'list->queue) ) ) )
(##sys#length lst0)) )
; (queue-push-back! queue item)
; Pushes an item into the first position of a queue.
(define (queue-push-back! q item) ; thread-safe
(##sys#check-structure q 'queue 'queue-push-back!)
(let ((newlist (cons item (##sys#slot q 1))))
(##sys#setslot q 1 newlist)
(if (eq? '() (##sys#slot q 2))
(##sys#setslot q 2 newlist))
(##sys#setislot q 3 (fx+ (##sys#slot q 3) 1))))
; (queue-push-back-list! queue item-list)
; Pushes the items in item-list back onto the queue,
; so that (car item-list) becomes the next removable item.
(define-inline (last-pair lst0)
(do ((lst lst0 (##sys#slot lst 1)))
((eq? (##sys#slot lst 1) '()) lst)))
(define (queue-push-back-list! q itemlist)
(##sys#check-structure q 'queue 'queue-push-back-list!)
(##sys#check-list itemlist 'queue-push-back-list!)
(let* ((newlist (append itemlist (##sys#slot q 1)))
(newtail (if (eq? newlist '())
'()
(last-pair newlist))))
(##sys#setslot q 1 newlist)
(##sys#setslot q 2 newtail)
(##sys#setislot q 3 (fx+ (##sys#slot q 3) (##core#inline "C_i_length" itemlist)))))
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