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arity reduction

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Matthew Butterick 6 years ago
parent ae8c3e4937
commit 2a37208847
1 changed files with 81 additions and 36 deletions
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117
csp/csp.rkt
Unescape Escape View File

@ -20,8 +20,8 @@
[else
(match-define (cons name other-names) names)
(for/and ([val (in-list ($csp-vals csp name))])
;; todo: reconsider efficiency of currying every value
(($constraint other-names (curry proc val)) csp))])))
;; todo: reconsider efficiency of currying every value
(($constraint other-names (curry proc val)) csp))])))
(define/contract (check-name-in-csp! caller csp name)
(symbol? $csp? $var-name? . -> . void?)
@ -61,11 +61,11 @@
(($csp? procedure? (listof (listof $var-name?))) ((or/c #false $var-name?)) . ->* . void?)
(set-$csp-constraints! csp (append ($csp-constraints csp)
(for/list ([names (in-list namess)])
(for ([name (in-list names)])
(check-name-in-csp! 'add-constraint! csp name))
($constraint names (if proc-name
(procedure-rename proc proc-name)
proc))))))
(for ([name (in-list names)])
(check-name-in-csp! 'add-constraint! csp name))
($constraint names (if proc-name
(procedure-rename proc proc-name)
proc))))))
(define/contract (add-pairwise-constraint! csp proc var-names [proc-name #false])
(($csp? procedure? (listof $var-name?)) ($var-name?) . ->* . void?)
@ -78,7 +78,7 @@
(define/contract (no-solutions? csp)
($csp? . -> . boolean?)
(for/or ([var (in-list ($csp-vars csp))])
(empty? ($var-vals var))))
(empty? ($var-vals var))))
(struct inconsistency-error () #:transparent)
@ -86,14 +86,14 @@
($csp? unary-constraint? . -> . $csp?)
(match-define ($constraint (list constraint-name) proc) constraint)
(define new-csp ($csp (for/list ([var (in-list ($csp-vars csp))])
(match-define ($var name vals) var)
(if (eq? name constraint-name)
;; special rule: use promise for a constant value
;; to skip the filtering
($var name (if (promise? proc)
(force proc)
(filter proc vals)))
var))
(match-define ($var name vals) var)
(if (eq? name constraint-name)
;; special rule: use promise for a constant value
;; to skip the filtering
($var name (if (promise? proc)
(force proc)
(filter proc vals)))
var))
;; once the constraint is applied, it can go away
;; ps this is not the same as an "assigned" constraint
;; because the var may still have multiple values
@ -113,7 +113,7 @@
(check-name-in-csp! '$csp-vals csp name)
(for/first ([var (in-list ($csp-vars csp))]
#:when (eq? name ($var-name var)))
($var-vals var)))
($var-vals var)))
(struct $arc (name constraint) #:transparent)
@ -126,37 +126,37 @@
(λ (val other-val) (constraint-proc other-val val)))) ; otherwise reverse arg order
(define (satisfies-arc? val)
(for/or ([other-val (in-list ($csp-vals csp other-name))])
(proc val other-val)))
(proc val other-val)))
(apply-unary-constraint csp ($constraint (list name)
(procedure-rename
satisfies-arc?
(string->symbol (format "satisfies-arc-with-~a?" other-name))))))
(string->symbol (format "~a-arc-to-~a" (object-name proc) other-name))))))
(define/contract (binary-constraints->arcs constraints)
((listof binary-constraint?) . -> . (listof $arc?))
(for*/list ([constraint (in-list constraints)]
[name (in-list ($constraint-names constraint))])
($arc name constraint)))
($arc name constraint)))
(define/contract (terminating-at arcs name)
((listof $arc?) $var-name? . -> . (listof $arc?))
(for/list ([arc (in-list arcs)]
#:when (eq? name (second ($constraint-names ($arc-constraint arc)))))
arc))
arc))
(define/contract (constraint-assigned? csp constraint)
($csp? $constraint? . -> . any/c)
(for/and ([name (in-list ($constraint-names constraint))])
(memq name (map $var-name (assigned-vars csp)))))
(memq name (map $var-name (assigned-vars csp)))))
(define/contract (remove-assigned-constraints csp [arity #false])
(($csp?) (exact-nonnegative-integer?) . ->* . $csp?)
(($csp?) ((or/c #false exact-nonnegative-integer?)) . ->* . $csp?)
($csp
($csp-vars csp)
(for/list ([constraint (in-list ($csp-constraints csp))]
#:unless (and (if arity (= (length ($constraint-names constraint)) arity) #true)
(constraint-assigned? csp constraint)))
constraint)))
constraint)))
(define (remove-assigned-binary-constraints csp)
(remove-assigned-constraints csp 2))
@ -222,24 +222,69 @@
($constraint? $var-name? . -> . boolean?)
(and (memq name ($constraint-names constraint)) #true))
(define/contract (test-assignments csp)
(define/contract (validate-assignments csp)
($csp? . -> . $csp?)
(define assigned-names (map $var-name (assigned-vars csp)))
(for/fold ([csp csp])
([constraint (in-list ($csp-constraints csp))]
#:when (constraint-assigned? csp constraint))
(unless (constraint csp) (raise (inconsistency-error)))
(remove-assigned-constraints csp)))
(for ([constraint (in-list ($csp-constraints csp))]
#:when (constraint-assigned? csp constraint))
(unless (constraint csp) (raise (inconsistency-error))))
(reduce-constraint-arity (remove-assigned-constraints csp)))
(define/contract (assign-val csp name val)
($csp? $var-name? any/c . -> . $csp?)
(define csp-with-assignment (apply-unary-constraint csp ($constraint (list name) (delay (list val)))))
(test-assignments csp-with-assignment))
(validate-assignments csp-with-assignment))
(define (reduce-arity proc args)
(procedure-rename
(λ xs
(apply proc (for/fold ([acc empty]
[xs xs]
[vals (filter-not symbol? args)]
#:result (reverse acc))
([arg (in-list args)])
(if (symbol? arg)
(values (cons (car xs) acc) (cdr xs) vals)
(values (cons (car vals) acc) xs (cdr vals))))))
(string->symbol (format "reduced-arity-~a" (object-name proc)))))
(module+ test
(require rackunit)
(define f (λ (a b c d) (+ a b c d)))
(check-equal? 10 ((reduce-arity f '(1 b c d)) 2 3 4))
(check-equal? 10 ((reduce-arity f '(1 2 c d)) 3 4))
(check-equal? 10 ((reduce-arity f '(1 2 3 d)) 4))
(check-equal? 10 ((reduce-arity f '(1 b 3 d)) 2 4))
(check-equal? 10 ((reduce-arity f '(a b 3 d)) 1 2 4)))
(define/contract (reduce-constraint-arity csp [minimum-arity 3])
(($csp?) (exact-nonnegative-integer?) . ->* . $csp?)
(define assigned-names (map $var-name (assigned-vars csp)))
($csp ($csp-vars csp)
(for/list ([constraint (in-list ($csp-constraints csp))])
(match-define ($constraint cnames proc) constraint)
(cond
[(and (<= minimum-arity (length cnames))
(for/or ([cname (in-list cnames)])
(memq cname assigned-names)))
($constraint (for/list ([cname (in-list cnames)]
#:unless (memq cname assigned-names))
cname)
(reduce-arity proc (for/list ([cname (in-list cnames)])
(if (memq cname assigned-names)
(car ($csp-vals csp cname))
cname))))]
[else constraint]))))
(module+ test
(define creduce (assign-val ($csp (list ($var 'a '(1 2 3)) ($var 'b '(2 3)) ($var 'c '(1 2 3 4 5))) (list ($constraint '(a b c) (procedure-rename (λ (a b c) (= (+ a b c) 4)) 'summer)))) 'a 1))
(check-equal?
(make-arcs-consistent (reduce-constraint-arity creduce))
($csp (list ($var 'a '(1)) ($var 'b '(2)) ($var 'c '(1))) '())))
;; todo: inferences between assignments
(define/contract (infer csp)
($csp? . -> . $csp?)
(test-assignments (make-arcs-consistent csp)))
(validate-assignments (make-arcs-consistent csp)))
(define/contract (backtracking-solver csp)
($csp? . -> . generator?)
@ -250,15 +295,15 @@
[else ;; we have at least 1 unassigned var
(match-define ($var name vals) (select-unassigned-var csp))
(for ([val (in-list (order-domain-values vals))])
(with-handlers ([inconsistency-error? void])
(backtrack (infer (assign-val csp name val)))))]))))
(with-handlers ([inconsistency-error? void])
(backtrack (infer (assign-val csp name val)))))]))))
(define/contract (solve* csp [finish-proc values][solution-limit +inf.0])
(($csp?) (procedure? integer?) . ->* . (listof any/c))
(define solutions
(for/list ([solution (in-producer (backtracking-solver csp) (void))]
[idx (in-range solution-limit)])
(finish-proc solution)))
(finish-proc solution)))
(unless (pair? solutions) (raise (inconsistency-error)))
solutions)

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