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#lang racket/base
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(require racket/class sugar/container sugar/debug racket/contract racket/match racket/generator racket/list)
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(require "domain.rkt" "helper.rkt" "constraint.rkt" "solver.rkt")
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(provide (all-defined-out))
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(define/contract problem%
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;; Class used to define a problem and retrieve solutions
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(class/c [reset (->m void?)]
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[set-solver (solver%? . ->m . void?)]
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[get-solver (->m solver%?)]
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;; todo: tighten `object?` contract
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[add-variable (any/c (or/c list? domain%?) . ->m . void?)]
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[add-variables ((listof any/c) (or/c list? domain%?) . ->m . void?)]
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[add-constraint (((or/c constraint%? procedure?)) ((listof any/c)) . ->*m . void?)]
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[get-solution (->m any/c)]
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[get-solutions (->m list?)])
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(class* object% (printable<%>)
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(super-new)
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(init-field [solver #f])
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(field [_solver (or solver (new backtracking-solver%))]
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[_constraints #f]
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[_variable-domains #f])
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(reset) ; use method rather than manually set up fields
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;; implement object printing
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(define (repr) (format "<problem% ~a>" (hash-keys _variable-domains)))
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(define/public (custom-print out quoting-depth) (print (repr) out))
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(define/public (custom-display out) (displayln (repr) out))
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(define/public (custom-write out) (write (repr) out))
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(define/public (reset)
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;; Reset the current problem definition
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(set! _constraints null)
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(set! _variable-domains (make-hash)))
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(define/public (set-solver solver)
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;; Set the problem solver currently in use
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(set! _solver solver))
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(define/public (get-solver)
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;; Get the problem solver currently in use
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_solver)
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(define/public (add-variable variable domain-or-values)
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;; Add a variable to the problem
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;; Contract insures input is Domain object or list of values.
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(when (hash-has-key? _variable-domains variable)
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(error 'add-variable (format "Tried to insert duplicated variable ~a" variable)))
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(define domain (if (domain%? domain-or-values)
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(send domain-or-values copy)
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(new domain% [set domain-or-values])))
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(when (null? (get-field _list domain))
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(error 'add-variable "domain value is null"))
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(hash-set! _variable-domains variable domain))
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(define/public (add-variables variables domain)
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;; Add one or more variables to the problem
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(define in-thing (cond
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[(string? variables) in-string]
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[(list? variables) in-list]
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[else (error 'add-variables (format "Don’t know what to do with ~a" variables))]))
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(for ([var (in-thing variables)])
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(add-variable var domain)))
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(define/public (add-constraint constraint-or-proc [variables null])
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;; Add a constraint to the problem
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;; contract guarantees input is procedure or constraint% object
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(define constraint (if (procedure? constraint-or-proc)
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(new function-constraint% [func constraint-or-proc])
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constraint-or-proc))
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(py-append! _constraints (list constraint variables)))
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(define-syntax-rule (solution-macro solution-proc null-proc)
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(begin
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(define-values (domains constraints vconstraints) (get-args))
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(if (null? domains)
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(if null-proc (null-proc null) null)
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(send _solver solution-proc domains constraints vconstraints))))
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(define/public (get-solution)
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;; Find and return a solution to the problem
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(solution-macro get-solution #f))
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(define/public (get-solutions)
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;; Find and return all solutions to the problem
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(solution-macro get-solutions #f))
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(define/public (get-solution-iter)
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; Return an iterator to the solutions of the problem
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(solution-macro get-solution-iter yield))
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(define (get-args)
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(define variable-domains (hash-copy _variable-domains))
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(define constraints
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(let ([all-variables (hash-keys variable-domains)])
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(for/list ([(constraint variables) (in-parallel (map first _constraints) (map second _constraints))])
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(list constraint (if (null? variables) all-variables variables)))))
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(define vconstraints
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(hash-copy ; converts for/hash to mutable hash
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(for/hash ([variable (in-hash-keys variable-domains)])
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(values variable null))))
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(for* ([(constraint variables) (in-parallel (map first constraints) (map second constraints))]
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[variable (in-list variables)])
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(hash-update! vconstraints variable (λ(val) (cons (list constraint variables) val))))
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(for ([(constraint variables) (in-parallel (map first constraints) (map second constraints))])
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(send constraint preprocess variables variable-domains constraints vconstraints))
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(if (for/or ([domain (in-hash-values variable-domains)])
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(send domain reset-state)
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(null? (get-field _list domain)))
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(values null null null)
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(values variable-domains constraints vconstraints))))) |