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#lang racket/base
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(require racket/class racket/contract racket/match racket/list racket/generator)
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(require sugar/container sugar/debug)
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(require "helpers.rkt")
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(module+ test (require rackunit))
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;; Adapted from work by Gustavo Niemeyer
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#|
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# Copyright (c) 2005-2014 - Gustavo Niemeyer <gustavo@niemeyer.net>
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#
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# 1. Redistributions of source code must retain the above copyright notice, this
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# list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
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# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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|#
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(provide (all-defined-out))
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;(provide Problem Variable Domain Unassigned Solver BacktrackingSolver RecursiveBacktrackingSolver MinConflictsSolver Constraint FunctionConstraint AllDifferentConstraint AllEqualConstraint MaxSumConstraint ExactSumConstraint MinSumConstraint InSetConstraint NotInSetConstraint SomeInSetConstraint SomeNotInSetConstraint)
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;(define Problem/c (λ(x) (is-a x Problem)))
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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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;; todo: tighten `object?` contracts
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[setSolver (object? . ->m . void?)]
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[getSolver (->m object?)]
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;; todo: tighten `object?` contract
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[addVariable (any/c (or/c list? object?) . ->m . void?)]
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[getSolutions (->m list?)])
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(class object%
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(super-new)
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(init-field [solver #f])
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(field [_solver (or solver (new BacktrackingSolver))]
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[_constraints null]
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[_variables (make-hash)])
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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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(hash-clear! _variables))
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(define/public (setSolver solver)
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;; Change the problem solver currently in use
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(set! _solver solver))
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(define/public (getSolver)
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;; Obtain the problem solver currently in use
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_solver)
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(define/public (addVariable variable domain)
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;; Add a variable to the problem
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(when (variable . in? . _variables)
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(error 'addVariable (format "Tried to insert duplicated variable ~a" variable)))
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(cond
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[(list? domain) (set! domain (new Domain [set domain]))]
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;; todo: test for `instance-of-Domain?` ; how to copy domain?
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[(object? domain) (set! domain '(copy.copy domain))]
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[else (error 'addVariable "Domains must be instances of subclasses of Domain")])
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(when (not (object? domain)) (error 'fudge))
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(when (not domain) ; todo: check this test
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(error 'addVariable "Domain is empty"))
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(hash-set! _variables variable domain))
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(define/public (addVariables variables domain)
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;; Add one or more variables to the problem
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(for-each (λ(var) (addVariable var domain)) variables))
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(define/public (getSolution)
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;; Find and return a solution to the problem
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(define-values (domains constraints vconstraints) (_getArgs))
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(if (not domains)
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null
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(send _solver getSolution domains constraints vconstraints)))
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(define/public (getSolutions)
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;; Find and return all solutions to the problem
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(define-values (domains constraints vconstraints) (_getArgs))
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(if (not domains)
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null
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(send _solver getSolutions domains constraints vconstraints)))
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(define/public (_getArgs)
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(define domains (hash-copy _variables))
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(define allvariables (hash-keys domains))
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(define constraints null)
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(for ([constraint-variables-pair (in-list _constraints)])
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(match-define (cons constraint variables) constraint-variables-pair)
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(when (not variables)
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(set! variables allvariables))
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(set! constraints (append constraints (list (cons constraint variables)))))
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(define vconstraints (make-hash))
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(for ([variable (in-hash-keys domains)])
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(hash-set! vconstraints variable null))
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(for ([constraint-variables-pair (in-list constraints)])
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(match-define (cons constraint variables) constraint-variables-pair)
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(for ([variable (in-list variables)])
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(hash-update! vconstraints variable (λ(val) (append val (list (cons constraint variables)))))))
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(for ([constraint-variables-pair (in-list constraints)])
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(match-define (cons constraint variables) constraint-variables-pair)
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(send constraint preProcess variables domains constraints vconstraints))
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(define result #f)
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(let/ec done
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(for ([domain (in-list (hash-values domains))])
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(send domain resetState)
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(when (not domain)
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(set! result (list null null null))
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(done)))
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(set! result (list domains constraints vconstraints)))
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(apply values result))
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))
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(module+ test
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(check-equal? (get-field _solver (new Problem [solver 'solver-in])) 'solver-in)
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(check-equal? (get-field _constraints (new Problem)) null)
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(check-equal? (get-field _variables (new Problem)) (make-hash))
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(define problem (new Problem)) ;; test from line 125
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(send problem addVariable "a" '(1))
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(check-equal? (get-field _list (hash-ref (get-field _variables problem) "a")) '(1))
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(displayln (format "The solution to ~a is ~a"
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problem
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(send problem getSolutions)))
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(send problem reset)
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(check-equal? (get-field _variables problem) (make-hash))
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(send problem addVariables '("a" "b") '(1 2 3))
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(check-equal? (get-field _list (hash-ref (get-field _variables problem) "a")) '(1 2 3))
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(check-equal? (get-field _list (hash-ref (get-field _variables problem) "b")) '(1 2 3))
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)
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;; ----------------------------------------------------------------------
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;; Domains
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;; ----------------------------------------------------------------------
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(define Domain
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;; Class used to control possible values for variables
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;; When list or tuples are used as domains, they are automatically
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;; converted to an instance of that class.
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(class* object% (printable<%>)
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(super-new)
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(init-field set)
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(field [_list set][_hidden null][_states null])
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(define (repr) (format "<Domain ~v>" _list))
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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 (resetState)
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;; Reset to the original domain state, including all possible values
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(py-extend! _list _hidden)
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(set! _hidden null)
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(set! _states null))
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(define/public (domain-pop!)
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(py-pop! _list))
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))
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;; ----------------------------------------------------------------------
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;; Solvers
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;; ----------------------------------------------------------------------
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(define Solver
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;; Abstract base class for solvers
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(class object%
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(super-new)
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(abstract getSolution)
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(abstract getSolutions)
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(abstract getSolutionIter)))
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(define BacktrackingSolver
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;; Problem solver with backtracking capabilities
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(class Solver
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(super-new)
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(init-field [forwardcheck #t])
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(field [_forwardcheck forwardcheck])
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(define/override (getSolutionIter domains constraints vconstraints)
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(define forwardcheck _forwardcheck)
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(define assignments (make-hash))
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(define queue null)
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(define values null)
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(define pushdomains null)
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(define variable #f)
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(let/ec done
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;; Mix the Degree and Minimum Remaing Values (MRV) heuristics
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(define lst (sort (for/list ([variable (in-hash-keys domains)])
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(list (* -1 (length (hash-ref vconstraints variable)))
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(length (get-field _list (hash-ref domains variable)))
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variable)) list-comparator))
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(report lst)
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(let/ec bonk
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(if (not (null? lst)) ; ? good translation of for–else?
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(for ([item (in-list lst)])
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(when (not ((last item) . in? . assignments))
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; Found unassigned variable
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(set! variable (last item))
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(set! values (hash-ref domains variable))
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(set! pushdomains
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(if forwardcheck
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(for/list ([x (in-hash-keys domains)]
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#:when (and (not (x . in? . assignments))
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(not (x . equal? . variable))))
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(hash-ref domains x))
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null))
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(bonk)))
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(begin
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;; No unassigned variables. We've got a solution. Go back
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;; to last variable, if there's one.
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(generator ()
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(yield (hash-copy assignments))
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(when (not queue) (done))
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(match-define (list variable values pushdomains) (py-pop! queue))
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(when (not (null? pushdomains))
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(for ([domain (in-list pushdomains)])
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(send domain popState)))))))
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(report variable)
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(report values)
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(report assignments)
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(let/ec inner-done
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;; We have a variable. Do we have any values left?
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(report values)
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(when (null? values)
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;; No. Go back to last variable, if there's one.
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(hash-remove! assignments variable)
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(let loop ()
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(if (not (null? queue))
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(let ()
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(define-values (variable values pushdomains) (py-pop! queue))
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(when pushdomains
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(for ([domain (in-list pushdomains)])
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(send domain popState)))
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(when values (inner-done))
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(hash-remove! assignments variable)
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(loop))
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(error 'todo "return from function"))))
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;; Got a value. Check it.
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(hash-set! assignments variable (send values domain-pop!))
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(when (not (null? pushdomains))
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(for ([domain (in-list pushdomains)])
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(send domain pushState)))
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;; todo: ok replacement for for/else?
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(if (not (null? (hash-ref vconstraints variable)))
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(for ([cvpair (in-list (hash-ref vconstraints variable))])
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(match-define (cons constraint variables) cvpair)
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(when (not (constraint variables domains assignments pushdomains))
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;; Value is not good.
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(inner-done)))
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(inner-done))
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(when (not (null? pushdomains))
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(for ([domain (in-list pushdomains)])
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(send domain popState)))
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;; Push state before looking for next variable.
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(py-append! queue (list variable values pushdomains))))
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(error 'getSolutionIter "Whoops, broken solver"))
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(define/override (getSolution domains constraints vconstraints)
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;; todo: fix this
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(void))
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(define/override (getSolutions domains constraints vconstraints)
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(for/list ([solution (in-generator (getSolutionIter domains constraints vconstraints))]) solution))
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))
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(module+ main
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(define p (new Problem))
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(define d (new Domain [set '(1 2)]))
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) |