Contents

#!/usr/bin/ruby

module ConstraintSolver
    # This class represents a solution to a constraint satisfaction problem.
    class Solution
	attr_reader :variables, :merit, :violation
	# Initialises a new solution with a list of variables. The variables
	# must all have values assigned to them.
	# Optionally, a map to map domain values of variables to their merit and
	# a number designating the cost of violating constraints in the solution can
	# be specified.
	def initialize(variables, meritMap={}, violation=0)
	    if not variables.kind_of?(Array)
		variables = Array.new([ variables ])
	    end
	    if variables.inject(true) { |res,var| res & var.assigned? }
		@variables = Array.new
		variables.each { |variable|
		    @variables << variable.dup
		}
	    else
		raise ArgumentError, "All variables must have values assigned to them!"
	    end
	    @merit = 0
	    @variables.each { |var|
		@merit += meritMap[var.value] ? var.merit * meritMap[var.value] : var.merit
	    }
	    @violation = violation
	    @merit -= @violation
	end

	def each
	    @variables.each { |variable|
		yield variable
	    }
	end

	def <=>(solution)
	    @value <=> solution.value
	end

	def ==(solution)
	    return false unless solution.kind_of?(Solution)
	    @variables == solution.variables and @merit == solution.merit and @violation == solution.violation
	end

	def to_s
	    s = (@variables.collect { |variable|
		variable.to_s
	    }).join(", ")
	    s += ", merit " + @merit.to_s unless @merit.nil?
	    s += ", violation " + @violation.to_s unless @violation.nil?
	    return s
	end
    end
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
ConstraintSolver-0.1	lib/Solution.rb