channel.rb in gecoder-0.8.3

- old
+ new

@@ -4,11 +4,11 @@
     # integer variable. Beyond the common options the channel constraint can
     # also take the following option:
     #
     # [:offset]  Specifies an offset for the integer variable. If the offset is
     #            set to k then the integer variable takes value i+k exactly 
-    #            when the variable at index i in the boolean enumration is true 
+    #            when the variable at index i in the boolean enumeration is true 
     #            and the rest are false.
     def channel(int_var, options = {})
       if @params[:negate]
         raise Gecode::MissingConstraintError, 'A negated channel constraint ' + 
           'is not implemented.'
@@ -23,37 +23,42 @@
       
       @params.update(:rhs => int_var, :offset => options.delete(:offset) || 0)
       @params.update(Gecode::Constraints::Util.decode_options(options))
       @model.add_constraint Channel::ChannelConstraint.new(@model, @params)
     end
+
+    # Adds a channel constraint on the variables in the enum with the specified 
+    # set variable.
+    provide_commutivity(:channel){ |rhs, _| rhs.kind_of? Gecode::FreeSetVar }
   end
   
   # A module that gathers the classes and modules used in channel constraints
   # involving one boolean enum and one integer variable.
   module Channel #:nodoc:
-    # Describes a channel constraint that "channels" an enumerations of 
+    # Describes a channel constraint that "channels" an enumeration of 
     # boolean variables with an integer variable. This constrains the integer
     # variable to take value i exactly when the variable at index i in the 
     # boolean enumeration is true and the others are false.
     # 
-    # Neither reification nor negation is supported.
+    # Neither reification nor negation is supported. The int variable
+    # and the enumeration can be interchanged.
     #
     # == Examples
     #
-    # # Constrains the enumeration called +selected_option+ to be false in the
+    # # Constrains the enumeration called +option_is_selected+ to be false in the
     # # first four positions and have exactly one true variable in the other. 
-    # selected_option.must.channel selected_option_index 
+    # option_is_selected.must.channel selected_option_index 
     # selected_option_index.must_be > 3
     #
-    # # Constrains the enumeration called +selected_option+ to be false in the
+    # # Constrains the enumeration called +option_is_selected+ to be false in the
     # # first five positions and have exactly one true variable in the other. 
-    # selected_option.must.channel(selected_option_index, :offset => 1) 
+    # selected_option_index.must.channel(option_is_selected, :offset => 1) 
     # selected_option_index.must_be > 3
     class ChannelConstraint < Gecode::Constraints::Constraint
       def post
         lhs, rhs, offset = @params.values_at(:lhs, :rhs, :offset)
         Gecode::Raw::channel(@model.active_space, lhs.to_bool_var_array, 
           rhs.bind, offset, *propagation_options)
       end
     end
   end
-end
\ No newline at end of file
+end