Gecode/R version 0.5.0 has been released. http://gecoder.rubyforge.org/ It's still in the development, so don't expect any form of backwards compatibility (things will change left and right if needed to). == What is Gecode/R? == Gecode/R is a Ruby interface to Gecode[1] which allows you to use constraint programming in Ruby. It's typically useful for problems where you otherwise have to do a search through various assignments to find a solution. All you have to do is describe the properties of solutions to a problem and Gecode will find them. == Installation == First install Gecode 1.3.1 (see installation[4] for links). And then do gem install gecoder == Features == See the website[5] for a more detailed list. * Finite domain integers, booleans and finite set variables. * Supports many of Gecode's integer constraints, all of the boolean constraints and some of the set constraints. * Reification and propagation strength. == Example == send+more=money is one of the many examples[2]. send + more ------ money The following assigns digits to each letter so that the above equation holds when the letter are substituted with the assigned digits. No two letters are assigned the same digit and the first letter of a word is not assigned 0 (so that no number starts with 0). class SendMoreMoney < Gecode::Model def initialize # Set up the variables, 8 letters with domain 0..9. s,e,n,d,m,o,r,y = @letters = int_var_array(8, 0..9) # Set up the constraints. # The equation must hold. (equation_row(s, e, n, d) + equation_row(m, o, r, e)).must == equation_row(m, o, n, e, y) # The initial letters may not be 0. s.must_not == 0 m.must_not == 0 # All letters must be assigned different digits. @letters.must_be.distinct # Set the branching. branch_on @letters, :variable => :smallest_size, :value => :min end def to_s %w{s e n d m o r y}.zip(@letters).map do |text, letter| "#{text}: #{letter.val}" end.join(', ') end private # A helper to make the linear equation a bit tidier. Takes a number of # variables and computes the linear combination as if the variable # were digits in a base 10 number. E.g. x,y,z becomes # 100*x + 10*y + z . def equation_row(*variables) variables.inject{ |result, variable| variable + result*10 } end end puts SendMoreMoney.new.solve!.to_s Output: s: 9, e: 5, n: 6, d: 7, m: 1, o: 0, r: 8, y: 2 == Learning more == The documentation[3] lists examples of all the available constraints and features (which in combination with the examples should get you going). Questions are welcome. == Changes since last announcement == === Version 0.5.0 / 11 July 2007 === This release adds set variables and some of their constraints, along with the last of the boolean constraints. * Added exclusive or and implication. * Added conjunction and disjunction for boolean enumerations. * Added set variables. They are created using Model{#set_var, #set_var_array, #set_var_matrix}. * Added domain constraints for set variables. * Added relation constraints for set variables. * Added set cardinality constraints. === Version 0.4.0 / 3 July 2007 === This release adds most of the integer variable constraints supported by Gecode. * [#11861] Fixed a bug stopping the creation of int variables with non-range domains. * Added domain constraints for int variables. * Added equality constraint for int enums. * Matrices of integer and boolean variables can now be created using Model#int_var_matrix Model#bool_var_matrix. * Added channel constraint for int enums. * Added element constraints (variable array access). * Added count constraints. * Added sortedness constraints. * Added arithmetic constraints (min, max, abs and variable multiplication). [1] http://www.gecode.org/ [2] http://gecoder.rubyforge.org/examples.html [3] http://gecoder.rubyforge.org/documentation/ [4] http://gecoder.rubyforge.org/installation.html [5] http://gecoder.rubyforge.org/features.html

on 2007-07-11 20:34