|
|
#lang debug racket
|
|
|
(require racket/generator graph sugar/debug)
|
|
|
(provide (all-defined-out))
|
|
|
|
|
|
(define-syntax when-debug
|
|
|
(let ()
|
|
|
(define debug #f)
|
|
|
(if debug
|
|
|
(make-rename-transformer #'begin)
|
|
|
(λ (stx) (syntax-case stx ()
|
|
|
[(_ . rest) #'(void)])))))
|
|
|
|
|
|
(define-syntax-rule (in-cartesian x)
|
|
|
(in-generator (let ([argss x])
|
|
|
(let loop ([argss argss][acc empty])
|
|
|
(if (null? argss)
|
|
|
(yield (reverse acc))
|
|
|
(for ([arg (in-list (car argss))])
|
|
|
(loop (cdr argss) (cons arg acc))))))))
|
|
|
|
|
|
(struct $csp (vars
|
|
|
constraints
|
|
|
[assignments #:auto]
|
|
|
[checks #:auto]) #:mutable #:transparent
|
|
|
#:auto-value 0)
|
|
|
(define csp? $csp?)
|
|
|
(define vars $csp-vars)
|
|
|
(define constraints $csp-constraints)
|
|
|
(define-syntax-rule (in-constraints csp) (in-list ($csp-constraints csp)))
|
|
|
(define-syntax-rule (in-vars csp) (in-list ($csp-vars csp)))
|
|
|
(define-syntax-rule (in-var-names csp) (in-list (map $var-name ($csp-vars csp))))
|
|
|
|
|
|
(struct $constraint (names proc) #:transparent
|
|
|
#:property prop:procedure
|
|
|
(λ (constraint csp)
|
|
|
(unless ($csp? csp)
|
|
|
(raise-argument-error '$constraint-proc "$csp" csp))
|
|
|
;; apply proc in many-to-many style
|
|
|
(for/and ([args (in-cartesian (map (λ (cname) ($csp-vals csp cname)) ($constraint-names constraint)))])
|
|
|
(apply ($constraint-proc constraint) args))))
|
|
|
|
|
|
(define (make-constraint [names null] [proc values])
|
|
|
($constraint names proc))
|
|
|
|
|
|
(define constraint-names $constraint-names)
|
|
|
(define constraint? $constraint?)
|
|
|
|
|
|
(define (csp->graphviz csp)
|
|
|
(define g (csp->graph csp))
|
|
|
(graphviz g #:colors (coloring/brelaz g)))
|
|
|
|
|
|
(define (csp->graph csp)
|
|
|
(for*/fold ([g (unweighted-graph/undirected (map var-name (vars csp)))])
|
|
|
([constraint (in-constraints csp)]
|
|
|
[edge (in-combinations (constraint-names constraint) 2)])
|
|
|
(apply add-edge! g edge)
|
|
|
g))
|
|
|
|
|
|
(struct $var (name domain) #:transparent)
|
|
|
(define var? $var?)
|
|
|
(define name? symbol?)
|
|
|
(define $var-vals $var-domain)
|
|
|
(define var-name $var-name)
|
|
|
|
|
|
(struct $cvar $var (past) #:transparent)
|
|
|
(struct $avar $var () #:transparent)
|
|
|
(define assigned-var? $avar?)
|
|
|
|
|
|
(define/contract (make-csp [vars null] [constraints null])
|
|
|
(() ((listof var?) (listof constraint?)) . ->* . csp?)
|
|
|
($csp vars constraints))
|
|
|
|
|
|
(define/contract (add-vars! csp names-or-procedure [vals-or-procedure empty])
|
|
|
((csp? (or/c (listof name?) procedure?)) ((or/c (listof any/c) procedure?)) . ->* . void?)
|
|
|
(for/fold ([vars ($csp-vars csp)]
|
|
|
#:result (set-$csp-vars! csp vars))
|
|
|
([name (in-list (if (procedure? names-or-procedure)
|
|
|
(names-or-procedure)
|
|
|
names-or-procedure))])
|
|
|
(when (memq name (map var-name vars))
|
|
|
(raise-argument-error 'add-vars! "var that doesn't already exist" name))
|
|
|
(append vars (list ($var name
|
|
|
(if (procedure? vals-or-procedure)
|
|
|
(vals-or-procedure)
|
|
|
vals-or-procedure))))))
|
|
|
|
|
|
(define/contract (add-var! csp name [vals-or-procedure empty])
|
|
|
((csp? name?) ((or/c (listof any/c) procedure?)) . ->* . void?)
|
|
|
(add-vars! csp (list name) vals-or-procedure))
|
|
|
|
|
|
(define/contract (add-constraints! csp proc namess [proc-name #false])
|
|
|
((csp? procedure? (listof (listof name?))) ((or/c #false name?)) . ->* . void?)
|
|
|
(set-$csp-constraints! csp (append (constraints csp)
|
|
|
(for/list ([names (in-list namess)])
|
|
|
(for ([name (in-list names)])
|
|
|
(check-name-in-csp! 'add-constraints! csp name))
|
|
|
(make-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 name?)) (name?) . ->* . void?)
|
|
|
(add-constraints! csp proc (combinations var-names 2) proc-name))
|
|
|
|
|
|
(define/contract (add-constraint! csp proc var-names [proc-name #false])
|
|
|
((csp? procedure? (listof name?)) (name?) . ->* . void?)
|
|
|
(add-constraints! csp proc (list var-names) proc-name))
|
|
|
|
|
|
(define/contract (alldiff= x y)
|
|
|
(any/c any/c . -> . boolean?)
|
|
|
(not (= x y)))
|
|
|
|
|
|
(struct $backtrack (names) #:transparent)
|
|
|
(define (backtrack! [names null]) (raise ($backtrack names)))
|
|
|
|
|
|
(define current-select-variable (make-parameter #f))
|
|
|
(define current-order-values (make-parameter #f))
|
|
|
(define current-inference (make-parameter #f))
|
|
|
(define current-solver (make-parameter #f))
|
|
|
(define current-shuffle (make-parameter #t))
|
|
|
|
|
|
(define/contract (check-name-in-csp! caller csp name)
|
|
|
(symbol? csp? name? . -> . void?)
|
|
|
(define names (map var-name (vars csp)))
|
|
|
(unless (memq name names)
|
|
|
(raise-argument-error caller (format "one of these existing csp var names: ~v" names) name)))
|
|
|
|
|
|
(define/contract (csp-var csp name)
|
|
|
(csp? name? . -> . $var?)
|
|
|
(check-name-in-csp! 'csp-var csp name)
|
|
|
(for/first ([var (in-vars csp)]
|
|
|
#:when (eq? name (var-name var)))
|
|
|
var))
|
|
|
|
|
|
(define/contract ($csp-vals csp name)
|
|
|
(csp? name? . -> . (listof any/c))
|
|
|
(check-name-in-csp! 'csp-vals csp name)
|
|
|
($var-domain (csp-var csp name)))
|
|
|
|
|
|
(define order-domain-values values)
|
|
|
|
|
|
(define/contract (assigned-name? csp name)
|
|
|
(csp? name? . -> . any/c)
|
|
|
(for/or ([var (in-vars csp)]
|
|
|
#:when (assigned-var? var))
|
|
|
(eq? name (var-name var))))
|
|
|
|
|
|
(define (reduce-function-arity proc pattern)
|
|
|
(unless (match (procedure-arity proc)
|
|
|
[(arity-at-least val) (<= val (length pattern))]
|
|
|
[(? number? val) (= val (length pattern))])
|
|
|
(raise-argument-error 'reduce-arity (format "list of length ~a, same as procedure arity" (procedure-arity proc)) pattern))
|
|
|
(define reduced-arity-name (string->symbol (format "reduced-arity-~a" (object-name proc))))
|
|
|
(define-values (boxed-id-names vals) (partition box? pattern))
|
|
|
(define new-arity (length boxed-id-names))
|
|
|
(procedure-rename
|
|
|
(λ xs
|
|
|
(unless (= (length xs) new-arity)
|
|
|
(apply raise-arity-error reduced-arity-name new-arity xs))
|
|
|
(apply proc (for/fold ([acc empty]
|
|
|
[xs xs]
|
|
|
[vals vals]
|
|
|
#:result (reverse acc))
|
|
|
([pat-item (in-list pattern)])
|
|
|
(if (box? pat-item)
|
|
|
(values (cons (car xs) acc) (cdr xs) vals)
|
|
|
(values (cons (car vals) acc) xs (cdr vals))))))
|
|
|
reduced-arity-name))
|
|
|
|
|
|
(define/contract (reduce-constraint-arity csp [minimum-arity 3])
|
|
|
((csp?) ((or/c #false exact-nonnegative-integer?)) . ->* . csp?)
|
|
|
(let ([assigned-name? (curry assigned-name? csp)])
|
|
|
(define (partially-assigned? constraint)
|
|
|
(ormap assigned-name? ($constraint-names constraint)))
|
|
|
(make-csp (vars csp)
|
|
|
(for/list ([constraint (in-constraints csp)])
|
|
|
(cond
|
|
|
[(and (if minimum-arity (<= minimum-arity (constraint-arity constraint)) #true)
|
|
|
(partially-assigned? constraint))
|
|
|
(match-define ($constraint cnames proc) constraint)
|
|
|
($constraint (filter-not assigned-name? cnames)
|
|
|
;; pattern is mix of values and boxed symbols (indicating variables to persist)
|
|
|
;; use boxes here as cheap way to distinguish id symbols from value symbols
|
|
|
(let ([reduce-arity-pattern (for/list ([cname (in-list cnames)])
|
|
|
(if (assigned-name? cname)
|
|
|
(first ($csp-vals csp cname))
|
|
|
(box cname)))])
|
|
|
(reduce-function-arity proc reduce-arity-pattern)))]
|
|
|
[else constraint])))))
|
|
|
|
|
|
(define nassns 0)
|
|
|
(define (reset-assns!) (set! nassns 0))
|
|
|
(define/contract (assign-val csp name val)
|
|
|
(csp? name? any/c . -> . csp?)
|
|
|
(when-debug (set! nassns (add1 nassns)))
|
|
|
(make-csp
|
|
|
(for/list ([var (vars csp)])
|
|
|
(if (eq? name (var-name var))
|
|
|
($avar name (list val))
|
|
|
var))
|
|
|
(constraints csp)))
|
|
|
|
|
|
(define/contract (unassigned-vars csp)
|
|
|
(csp? . -> . (listof (and/c $var? (not/c assigned-var?))))
|
|
|
(filter-not assigned-var? (vars csp)))
|
|
|
|
|
|
(define/contract (first-unassigned-variable csp)
|
|
|
(csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
|
|
|
(match (unassigned-vars csp)
|
|
|
[(? empty?) #false]
|
|
|
[(cons x _) x]))
|
|
|
|
|
|
(define/contract (minimum-remaining-values csp)
|
|
|
(csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
|
|
|
(match (unassigned-vars csp)
|
|
|
[(? empty?) #false]
|
|
|
[xs (argmin (λ (var) (length ($var-domain var))) (shuffle xs))]))
|
|
|
|
|
|
(define mrv minimum-remaining-values)
|
|
|
|
|
|
(define/contract (var-degree csp var)
|
|
|
(csp? $var? . -> . exact-nonnegative-integer?)
|
|
|
(for/sum ([constraint (in-constraints csp)]
|
|
|
#:when (memq (var-name var) ($constraint-names constraint)))
|
|
|
1))
|
|
|
|
|
|
(define/contract (blended-variable-selector csp)
|
|
|
(csp? . -> . (or/c #false (and/c $var? (not/c assigned-var?))))
|
|
|
(define uvars (unassigned-vars csp))
|
|
|
(cond
|
|
|
[(empty? uvars) #false]
|
|
|
[(findf singleton-var? uvars)]
|
|
|
[else (first (let* ([uvars-by-mrv (sort uvars < #:key (λ (var) (length ($var-domain var))))]
|
|
|
[uvars-by-degree (sort uvars-by-mrv > #:key (λ (var) (var-degree csp var)))])
|
|
|
uvars-by-degree))]))
|
|
|
|
|
|
(define/contract (remaining-values var)
|
|
|
($var? . -> . exact-nonnegative-integer?)
|
|
|
(length ($var-vals var)))
|
|
|
|
|
|
(define/contract (mrv-degree-hybrid csp)
|
|
|
(csp? . -> . (or/c #f $var?))
|
|
|
(define uvars (unassigned-vars csp))
|
|
|
(cond
|
|
|
[(empty? uvars) #false]
|
|
|
[else
|
|
|
;; minimum remaining values (MRV) rule
|
|
|
(define mrv-arg (argmin remaining-values uvars))
|
|
|
(match (filter (λ (var) (= (remaining-values mrv-arg) (remaining-values var))) uvars)
|
|
|
[(list winning-uvar) winning-uvar]
|
|
|
[(list mrv-uvars ...)
|
|
|
;; use degree as tiebreaker for mrv
|
|
|
(define max-degree-arg (argmax (λ (var) (var-degree csp var)) mrv-uvars))
|
|
|
;; use random tiebreaker for degree
|
|
|
(first (shuffle (filter (λ (var) (= (var-degree csp max-degree-arg) (var-degree csp var))) mrv-uvars)))])]))
|
|
|
|
|
|
(define first-domain-value values)
|
|
|
|
|
|
(define (no-inference csp name) csp)
|
|
|
|
|
|
(define/contract (relating-only constraints names)
|
|
|
((listof $constraint?) (listof name?) . -> . (listof $constraint?))
|
|
|
(for*/list ([constraint (in-list constraints)]
|
|
|
[cnames (in-value ($constraint-names constraint))]
|
|
|
#:when (and (= (length names) (length cnames))
|
|
|
(for/and ([name (in-list names)])
|
|
|
(memq name cnames))))
|
|
|
constraint))
|
|
|
|
|
|
(define (binary-constraint? constraint)
|
|
|
(= 2 (constraint-arity constraint)))
|
|
|
|
|
|
(define (constraint-relates? constraint name)
|
|
|
(memq name ($constraint-names constraint)))
|
|
|
|
|
|
(define nfchecks 0)
|
|
|
(define (reset-nfcs!) (set! nfchecks 0))
|
|
|
|
|
|
(define/contract (forward-check csp aname)
|
|
|
(csp? name? . -> . csp?)
|
|
|
(define aval (first ($csp-vals csp aname)))
|
|
|
(define (check-var var)
|
|
|
(match var
|
|
|
;; don't check against assigned vars, or the reference var
|
|
|
;; (which is probably assigned but maybe not)
|
|
|
[(? (λ (x) (or (assigned-var? x) (eq? (var-name x) aname)))) var]
|
|
|
[($var name vals)
|
|
|
(match ((constraints csp) . relating-only . (list aname name))
|
|
|
[(? empty?) var]
|
|
|
[constraints
|
|
|
(define new-vals
|
|
|
(for/list ([val (in-list vals)]
|
|
|
#:when (for/and ([constraint (in-list constraints)])
|
|
|
(let ([proc ($constraint-proc constraint)])
|
|
|
(if (eq? name (first ($constraint-names constraint)))
|
|
|
(proc val aval)
|
|
|
(proc aval val)))))
|
|
|
val))
|
|
|
($cvar name new-vals (cons aname (if ($cvar? var)
|
|
|
($cvar-past var)
|
|
|
null)))])]))
|
|
|
(define checked-vars (map check-var (vars csp)))
|
|
|
(when-debug (set! nfchecks (+ (length checked-vars) nchecks)))
|
|
|
;; conflict-set will be empty if there are no empty domains
|
|
|
(define conflict-set (for*/list ([var (in-list checked-vars)]
|
|
|
#:when (empty? ($var-domain var))
|
|
|
[name (in-list ($cvar-past var))])
|
|
|
name))
|
|
|
;; for conflict-directed backjumping it's essential to forward-check ALL vars
|
|
|
;; (even after an empty domain is generated) and combine their conflicts
|
|
|
;; so we can discover the *most recent past var* that could be the culprit.
|
|
|
;; If we just bail out at the first conflict, we may backjump too far based on its history
|
|
|
;; (and thereby miss parts of the search tree)
|
|
|
(when (pair? conflict-set)
|
|
|
(backtrack! conflict-set))
|
|
|
;; Discard constraints that have produced singleton domains
|
|
|
;; (they have no further use)
|
|
|
(define nonsingleton-constraints
|
|
|
(for/list ([constraint (in-constraints csp)]
|
|
|
#:unless (and
|
|
|
(binary-constraint? constraint)
|
|
|
(constraint-relates? constraint aname)
|
|
|
(let ([other-name (first (remq aname ($constraint-names constraint)))])
|
|
|
(singleton-var? (csp-var csp other-name)))))
|
|
|
constraint))
|
|
|
(make-csp checked-vars nonsingleton-constraints))
|
|
|
|
|
|
(define/contract (constraint-checkable? c names)
|
|
|
($constraint? (listof name?) . -> . any/c)
|
|
|
(for/and ([cname (in-list ($constraint-names c))])
|
|
|
(memq cname names)))
|
|
|
|
|
|
(define/contract (constraint-arity constraint)
|
|
|
($constraint? . -> . exact-nonnegative-integer?)
|
|
|
(length ($constraint-names constraint)))
|
|
|
|
|
|
(define (singleton-var? var)
|
|
|
(= 1 (length ($var-domain var))))
|
|
|
|
|
|
(define nchecks 0)
|
|
|
(define (reset-nchecks!) (set! nchecks 0))
|
|
|
(define/contract (check-constraints csp [mandatory-names #f] #:conflicts [conflict-count? #f])
|
|
|
((csp?) ((listof name?) #:conflicts boolean?) . ->* . (or/c csp? exact-nonnegative-integer?))
|
|
|
;; this time, we're not limited to assigned variables
|
|
|
;; (that is, vars that have been deliberately assigned in the backtrack process thus far)
|
|
|
;; we also want to use "singleton" vars (that is, vars that have been reduced to a single domain value by forward checking)
|
|
|
(define singleton-varnames (for/list ([var (in-vars csp)]
|
|
|
#:when (singleton-var? var))
|
|
|
(var-name var)))
|
|
|
(define-values (checkable-constraints other-constraints)
|
|
|
(partition (λ (c) (and (constraint-checkable? c singleton-varnames)
|
|
|
(if mandatory-names
|
|
|
(for/and ([name (in-list mandatory-names)])
|
|
|
(constraint-relates? c name))
|
|
|
#true))) (constraints csp)))
|
|
|
(cond
|
|
|
[conflict-count? (define conflict-count
|
|
|
(for/sum ([constraint (in-list checkable-constraints)]
|
|
|
#:unless (constraint csp))
|
|
|
1))
|
|
|
(when-debug (set! nchecks (+ conflict-count nchecks)))
|
|
|
conflict-count]
|
|
|
[else (for ([(constraint idx) (in-indexed (sort checkable-constraints < #:key constraint-arity))]
|
|
|
#:unless (constraint csp))
|
|
|
(when-debug (set! nchecks (+ (add1 idx) nchecks)))
|
|
|
(backtrack!))
|
|
|
;; discard checked constraints, since they have no further reason to live
|
|
|
(make-csp (vars csp) other-constraints)]))
|
|
|
|
|
|
(define/contract (make-nodes-consistent csp)
|
|
|
(csp? . -> . csp?)
|
|
|
;; todo: why does this function slow down searches?
|
|
|
(make-csp
|
|
|
(for/list ([var (in-vars csp)])
|
|
|
(match-define ($var name vals) var)
|
|
|
(define procs (for*/list ([constraint (in-constraints csp)]
|
|
|
[cnames (in-value ($constraint-names constraint))]
|
|
|
#:when (and (= 1 (length cnames)) (eq? name (car cnames))))
|
|
|
($constraint-proc constraint)))
|
|
|
($var name
|
|
|
(for*/fold ([vals vals])
|
|
|
([proc (in-list procs)])
|
|
|
(filter proc vals))))
|
|
|
(constraints csp)))
|
|
|
|
|
|
(define/contract (backtracking-solver
|
|
|
csp
|
|
|
#:select-variable [select-unassigned-variable
|
|
|
(or (current-select-variable) first-unassigned-variable)]
|
|
|
#:order-values [order-domain-values (or (current-order-values) first-domain-value)]
|
|
|
#:inference [inference (or (current-inference) no-inference)])
|
|
|
((csp?) (#:select-variable procedure? #:order-values procedure? #:inference procedure?) . ->* . generator?)
|
|
|
(generator ()
|
|
|
(let loop ([csp csp])
|
|
|
(match (select-unassigned-variable csp)
|
|
|
[#false (yield csp)]
|
|
|
[($var name domain)
|
|
|
(define (wants-backtrack? exn)
|
|
|
(and ($backtrack? exn) (or (let ([btns ($backtrack-names exn)])
|
|
|
(or (empty? btns) (memq name btns))))))
|
|
|
(for/fold ([conflicts null]
|
|
|
#:result (void))
|
|
|
([val (in-list (order-domain-values domain))])
|
|
|
(with-handlers ([wants-backtrack?
|
|
|
(λ (bt) (append conflicts (remq name ($backtrack-names bt))))])
|
|
|
(let* ([csp (assign-val csp name val)]
|
|
|
;; reduce constraints before inference,
|
|
|
;; to create more forward-checkable (binary) constraints
|
|
|
[csp (reduce-constraint-arity csp)]
|
|
|
[csp (inference csp name)]
|
|
|
[csp (check-constraints csp)])
|
|
|
(loop csp)))
|
|
|
conflicts)]))))
|
|
|
|
|
|
|
|
|
(define/contract (min-conflicts csp [max-steps 64])
|
|
|
(($csp?) (integer?) . ->* . generator?)
|
|
|
;; Solve a CSP by stochastic hillclimbing on the number of conflicts.
|
|
|
(generator ()
|
|
|
(let loop ([csp0 csp])
|
|
|
;; Generate a complete assignment for all variables (probably with conflicts)
|
|
|
(define starting-assignment
|
|
|
(for/fold ([csp csp0])
|
|
|
([var (in-vars csp0)])
|
|
|
(define name (var-name var))
|
|
|
(assign-val csp name (first (shuffle ($csp-vals csp0 name))))))
|
|
|
;; Now repeatedly choose a random conflicted variable and change it
|
|
|
(for/fold ([csp starting-assignment])
|
|
|
([i (in-range max-steps)])
|
|
|
(match (conflicted-var-names csp)
|
|
|
[(? empty?) (when (check-constraints csp) (yield csp)) (loop csp0)]
|
|
|
[cvar-names
|
|
|
(define cvar-name (first ((if (current-shuffle) shuffle values) cvar-names)))
|
|
|
(define val (min-conflicts-value csp cvar-name ($csp-vals csp0 cvar-name)))
|
|
|
(assign-val csp cvar-name val)]))
|
|
|
(loop csp0))))
|
|
|
|
|
|
(define/contract (conflicted-var-names csp)
|
|
|
($csp? . -> . (listof name?))
|
|
|
;; Return a list of variables in current assignment that are conflicted
|
|
|
(for/list ([name (in-var-names csp)]
|
|
|
#:when (positive? (nconflicts csp name)))
|
|
|
name))
|
|
|
|
|
|
(define/contract (min-conflicts-value csp name vals)
|
|
|
($csp? name? (listof any/c) . -> . any/c)
|
|
|
;; Return the value that will give var the least number of conflicts
|
|
|
(argmin (λ (val) (nconflicts csp name val)) (shuffle vals)))
|
|
|
|
|
|
(define no-value-sig (gensym))
|
|
|
|
|
|
(define/contract (nconflicts csp name [val no-value-sig])
|
|
|
(($csp? name?) (any/c) . ->* . exact-nonnegative-integer?)
|
|
|
;; How many conflicts var: val assignment has with other variables.
|
|
|
(check-constraints (if (eq? val no-value-sig)
|
|
|
csp
|
|
|
(assign-val csp name val)) (list name) #:conflicts #true))
|
|
|
|
|
|
(define/contract (csp->assocs csp)
|
|
|
(csp? . -> . (listof (cons/c name? any/c)))
|
|
|
(for/list ([var (in-vars csp)])
|
|
|
(match var
|
|
|
[($var name domain) (cons name (first domain))])))
|
|
|
|
|
|
(define/contract (solve* csp
|
|
|
#:finish-proc [finish-proc csp->assocs]
|
|
|
#:solver [solver (or (current-solver) backtracking-solver)]
|
|
|
#:limit [max-solutions +inf.0])
|
|
|
((csp?) (#:finish-proc procedure? #:solver procedure? #:limit integer?) . ->* . (listof any/c))
|
|
|
(when-debug
|
|
|
(reset-assns!)
|
|
|
(reset-nfcs!)
|
|
|
(reset-nchecks!))
|
|
|
(for/list ([solution (in-producer (solver csp) (void))]
|
|
|
[idx (in-range max-solutions)])
|
|
|
(finish-proc solution)))
|
|
|
|
|
|
(define/contract (solve csp
|
|
|
#:finish-proc [finish-proc csp->assocs]
|
|
|
#:solver [solver (or (current-solver) backtracking-solver)])
|
|
|
((csp?) (#:finish-proc procedure? #:solver procedure?) . ->* . (or/c #false any/c))
|
|
|
(match (solve* csp #:finish-proc finish-proc #:solver solver #:limit 1)
|
|
|
[(list solution) solution]
|
|
|
[else #false]))
|
|
|
|
|
|
(define (<> a b) (not (= a b)))
|
|
|
(define (neq? a b) (not (eq? a b)))
|
|
|
|