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typesetting/csp/constraint.rkt

205 lines
7.8 KiB
Racket

#lang racket/base
(require racket/class racket/contract racket/match)
(require sugar/container sugar/debug)
(module+ test (require rackunit))
;; Adapted from work by Gustavo Niemeyer
#|
# Copyright (c) 2005-2014 - Gustavo Niemeyer <gustavo@niemeyer.net>
#
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice, this
# list of conditions and the following disclaimer.
# 2. 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.
#
# 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 OWNER 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.
|#
(provide (all-defined-out))
;(provide Problem Variable Domain Unassigned Solver BacktrackingSolver RecursiveBacktrackingSolver MinConflictsSolver Constraint FunctionConstraint AllDifferentConstraint AllEqualConstraint MaxSumConstraint ExactSumConstraint MinSumConstraint InSetConstraint NotInSetConstraint SomeInSetConstraint SomeNotInSetConstraint)
;(define Problem/c (λ(x) (is-a x Problem)))
(define/contract Problem
;; Class used to define a problem and retrieve solutions
(class/c [reset (->m void?)]
;; todo: tighten `object?` contracts
[setSolver (object? . ->m . void?)]
[getSolver (->m object?)]
;; todo: tighten `object?` contract
[addVariable (any/c (or/c list? object?) . ->m . void?)]
[getSolutions (->m list?)])
(class object%
(super-new)
(init-field [solver #f])
(field [_solver (or solver (new BacktrackingSolver))]
[_constraints null]
[_variables (make-hash)])
(define/public (reset)
;; Reset the current problem definition
(set! _constraints null)
(hash-clear! _variables))
(define/public (setSolver solver)
;; Change the problem solver currently in use
(set! _solver solver))
(define/public (getSolver)
;; Obtain the problem solver currently in use
_solver)
(define/public (addVariable variable domain)
;; Add a variable to the problem
(when (variable . in? . _variables)
(error 'addVariable (format "Tried to insert duplicated variable ~a" variable)))
(cond
[(list? domain) (set! domain (new Domain [set domain]))]
;; todo: test for `instance-of-Domain?` ; how to copy domain?
[(object? domain) (set! domain '(copy.copy domain))]
[else (error 'addVariable "Domains must be instances of subclasses of Domain")])
(when (not (object? domain)) (error 'fudge))
(when (not domain) ; todo: check this test
(error 'addVariable "Domain is empty"))
(hash-set! _variables variable domain))
(define/public (addVariables variables domain)
;; Add one or more variables to the problem
(for-each (λ(var) (addVariable var domain)) variables))
(define/public (getSolutions)
;; Find and return all solutions to the problem
(define-values (domains constraints vconstraints) (_getArgs))
(if (not domains)
null
(send _solver getSolutions domains constraints vconstraints)))
(define/public (_getArgs)
(define domains (hash-copy _variables))
(define allvariables (hash-keys domains))
(define constraints null)
(for ([constraint-variables-pair (in-list _constraints)])
(match-define (cons constraint variables) constraint-variables-pair)
(when (not variables)
(set! variables allvariables))
(set! constraints (append constraints (list (cons 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 (cons constraint variables) constraint-variables-pair)
(for ([variable (in-list variables)])
(hash-update! vconstraints variable (λ(val) (append val (list (cons constraint variables)))))))
(for ([constraint-variables-pair (in-list constraints)])
(match-define (cons 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))
))
(module+ test
(check-equal? (get-field _solver (new Problem [solver 'solver-in])) 'solver-in)
(check-equal? (get-field _constraints (new Problem)) null)
(check-equal? (get-field _variables (new Problem)) (make-hash))
(define problem (new Problem))
(send problem addVariable "a" '(1 2))
(check-equal? (get-field _list (hash-ref (get-field _variables problem) "a")) '(1 2))
(send problem reset)
(check-equal? (get-field _variables problem) (make-hash))
(send problem addVariables '("a" "b") '(1 2 3))
(check-equal? (get-field _list (hash-ref (get-field _variables problem) "a")) '(1 2 3))
(check-equal? (get-field _list (hash-ref (get-field _variables problem) "b")) '(1 2 3))
(get-field _variables problem)
(send problem getSolutions)
)
;; ----------------------------------------------------------------------
;; Domains
;; ----------------------------------------------------------------------
(define Domain
;; Class used to control possible values for variables
;; When list or tuples are used as domains, they are automatically
;; converted to an instance of that class.
(class object%
(super-new)
(init-field set)
(field [_list set][_hidden null][_states null])
(define/public (resetState)
;; Reset to the original domain state, including all possible values
(set! _list (append _list _hidden))
(set! _hidden null)
(set! _states null))
))
;; ----------------------------------------------------------------------
;; Solvers
;; ----------------------------------------------------------------------
(define Solver
;; Abstract base class for solvers
(class object%
(super-new)
(abstract getSolution)
(abstract getSolutions)
(abstract getSolutionIter)))
(define BacktrackingSolver
;; Problem solver with backtracking capabilities
(class Solver
(super-new)
(init-field [forwardCheck #t])
(define/override (getSolutionIter domains constraints vconstraints)
;; resume here
(void))
(define/override (getSolution domains constraints vconstraints)
;; todo: repair this properly
(car (getSolutions domains constraints vconstraints)))
(define/override (getSolutions domains constraints vconstraints)
(getSolutionIter domains constraints vconstraints))
))
(module+ main
(define p (new Problem))
(define d (new Domain [set '(1 2)]))
)