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typesetting/csp/problem.rkt

125 lines
5.2 KiB
Racket

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#lang racket/base
(require racket/class sugar/container sugar/debug racket/contract racket/match)
(require "domain.rkt" "helper.rkt" "constraint.rkt" "solver.rkt")
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(provide (all-defined-out))
(define/contract problem%
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;; Class used to define a problem and retrieve solutions
(class/c [reset (->m void?)]
[set-solver (solver%? . ->m . void?)]
[get-solver (->m solver%?)]
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;; todo: tighten `object?` contract
[add-variable (any/c (or/c list? domain%?) . ->m . void?)]
[add-variables ((listof any/c) (or/c list? domain%?) . ->m . void?)]
[add-constraint (((or/c constraint%? procedure?)) ((listof any/c)) . ->*m . void?)]
[get-solution (->m any/c)]
[get-solutions (->m list?)]
[_get-args (->m (values (listof domain%?) (listof constraint%?) (listof hash?)))])
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(class* object% (printable<%>)
(super-new)
(init-field [solver #f])
(field [_solver (or solver (new backtracking-solver%))]
[_constraints #f]
[_variables #f])
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(reset)
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(define (repr) (format "<problem% ~a>" (hash-keys _variables)))
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(define/public (custom-print out quoting-depth) (print (repr) out))
(define/public (custom-display out) (displayln (repr) out))
(define/public (custom-write out) (write (repr) out))
(define/public (reset)
;; Reset the current problem definition
(set! _constraints null)
(set! _variables (make-hash)))
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(define/public (set-solver solver)
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;; Change the problem solver currently in use
(set! _solver solver))
(define/public (get-solver)
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;; Obtain the problem solver currently in use
_solver)
(define/public (add-variable variable domain-or-values)
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;; Add a variable to the problem
;; Contract insures input is Domain object or list of values.
(when (hash-has-key? _variables variable)
(error 'add-variable (format "Tried to insert duplicated variable ~a" variable)))
(define domain (if (domain%? domain-or-values)
(send domain-or-values copy)
(new domain% [set domain-or-values])))
(when (not (object? domain)) (error 'add-variable "not a Domain object"))
(when (null? (get-field _list domain)) (error 'add-variable "domain value is null"))
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(hash-set! _variables variable domain))
(define/public (add-variables variables domain)
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;; Add one or more variables to the problem
(define listified-variables
(cond
[(string? variables) (map (λ(c) (format "~a" c)) (string->list variables))]
[else variables]))
(for-each (λ(var) (add-variable var domain)) listified-variables))
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(define/public (add-constraint constraint [variables null])
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;; Add a constraint to the problem
(when (not (constraint%? constraint))
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(if (procedure? constraint)
(set! constraint (new function-constraint% [func constraint]))
(error 'add-constraint "Constraints must be instances of class Constraint")))
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(py-append! _constraints (list constraint variables)))
(define/public (get-solution)
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;; Find and return a solution to the problem
(define-values (domains constraints vconstraints) (_get-args))
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(if (not domains)
null
(send _solver get-solution domains constraints vconstraints)))
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(define/public (get-solutions)
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;; Find and return all solutions to the problem
(define-values (domains constraints vconstraints) (_get-args))
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(if (not domains)
null
(send _solver get-solutions domains constraints vconstraints)))
(define/public (get-solution-iter)
; Return an iterator to the solutions of the problem
(void))
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(define/public (_get-args)
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(define domains (hash-copy _variables))
(define allvariables (hash-keys domains))
(define constraints null)
(for ([constraint-variables-pair (in-list _constraints)])
(match-define (list constraint variables) constraint-variables-pair)
(when (null? variables)
(set! variables allvariables))
(set! constraints (append constraints (list (list constraint variables)))))
(define vconstraints (make-hash))
(for ([variable (in-hash-keys domains)])
(hash-set! vconstraints variable null))
(for ([constraint-variables-pair (in-list constraints)])
(match-define (list constraint variables) constraint-variables-pair)
(for ([variable (in-list variables)])
(hash-update! vconstraints variable (λ(val) (append val (list (list constraint variables)))))))
(for ([constraint-variables-pair (in-list constraints)])
(match-define (list constraint variables) constraint-variables-pair)
(send constraint preProcess variables domains constraints vconstraints))
(define result #f)
(let/ec done
(for ([domain (in-list (hash-values domains))])
(send domain resetState)
(when (not domain)
(set! result (list null null null))
(done)))
(set! result (list domains constraints vconstraints)))
(apply values result))
))