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117 lines
4.8 KiB
Racket
117 lines
4.8 KiB
Racket
#lang racket/base
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(require racket/class sugar/container racket/contract racket/match "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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;; todo: tighten `object?` contracts
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[setSolver (Solver? . ->m . void?)]
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[getSolver (->m Solver?)]
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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% (printable<%>)
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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 (repr) (format "<Problem ~a>" (hash-keys _variables)))
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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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(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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(define listified-variables
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(cond
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[(string? variables) (map (λ(c) (format "~a" c)) (string->list variables))]
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[else variables]))
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(for-each (λ(var) (addVariable var domain)) listified-variables))
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(define/public (addConstraint constraint [variables null])
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;; Add a constraint to the problem
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(when (not (Constraint? constraint))
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(if (procedure? constraint)
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(set! constraint (new FunctionConstraint [func constraint]))
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(error 'addConstraint "Constraints must be instances of class Constraint")))
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(py-append! _constraints (list constraint 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 (list constraint variables) constraint-variables-pair)
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(when (null? variables)
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(set! variables allvariables))
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(set! constraints (append constraints (list (list 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 (list 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 (list constraint variables)))))))
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(for ([constraint-variables-pair (in-list constraints)])
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(match-define (list 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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)) |