require 'csp'
include CSP

problem = Problem.new
var1 = Variable.new('1', [1,2,3,4])
var2 = Variable.new('2', [1,2,3,4])
var3 = Variable.new('3', [1,2,3,4])
var4 = Variable.new('4', [1,2,3,4])

cons = []
cons.push(Constraint.new( Proc.new {|a,b| a != b}, [var1,var2]))
cons.push(Constraint.new( Proc.new {|a,b| a != b}, [var1,var3]))
cons.push(Constraint.new( Proc.new {|a,b| a != b}, [var1,var4]))
cons.push(Constraint.new( Proc.new {|a,b| a != b}, [var2,var3]))
cons.push(Constraint.new( Proc.new {|a,b| a != b}, [var2,var4]))
cons.push(Constraint.new( Proc.new {|a,b| a != b}, [var3,var4]))
cons.push(Constraint.new( Proc.new {|a,b| (a - b).abs != 1}, [var1,var2]))
cons.push(Constraint.new( Proc.new {|a,b| (a - b).abs != 1}, [var2,var3]))
cons.push(Constraint.new( Proc.new {|a,b| (a - b).abs != 1}, [var3,var4]))
cons.push(Constraint.new( Proc.new {|a,b| (a - b).abs != 2}, [var1,var3]))
cons.push(Constraint.new( Proc.new {|a,b| (a - b).abs != 2}, [var2,var4]))
cons.push(Constraint.new( Proc.new {|a,b| (a - b).abs != 3}, [var1,var4]))
cons.each do |c|
  problem.add_constraint(c)
end

solver = Solver.new(problem)
solver.set_ordering([var1,var2,var3,var4])
solver.solve