Rewrote cartesian_product to use Array#list_comprehension.

lib/combinatorics/cartesian_product/mixin.rb

@@ -1,4 +1,4 @@
-require 'combinatorics/generator'
+require 'combinatorics/list_comprehension'
 
 module Combinatorics
   module CartesianProduct
@@ -36,21 +36,13 @@ module Mixin
       #   
       # @see http://en.wikipedia.org/wiki/Cartesian_product
       #
-      def cartesian_product(other)
-        return enum_for(:cartprod,other) unless block_given?
+      def cartesian_product(*others,&block)
+        return enum_for(:cartesian_product,*others) unless block
 
-        unless other.kind_of?(Enumerable)
-          raise(TypeError, 'cartprod requires another Enumerable object')
-        end
+        # a single empty Set will result in an empty Set
+        return nil if (empty? || others.any?(&:empty?))
 
-        other.each do |x|
-          self.each do |y|
-            z = [y, x]
-            z.flatten!
-
-            yield z
-          end
-        end
+        Array[self,*others].comprehension(&block)
       end
 
       alias cartprod  cartesian_product

spec/cartesian_product/mixin_examples.rb

@@ -4,22 +4,22 @@
 
 shared_examples_for "CartesianProduct::Mixin" do
   it "the cartprod of any two Set's should return an Enumerator" do
-    set     = subject[]
+    set     = subject[1]
     results = set.cartprod(set)
 
     results.should be_kind_of(Enumerator)
   end
 
   it "the cartprod of two empty Set's should return an empty Set" do
     set     = subject[]
-    results = set.cartprod([[]]).to_a
+    results = set.cartprod([]).to_a
 
     results.should be_empty
   end
 
   it "the cartprod of a single empty set should return an empty Set" do
-    set     = subject[1]
-    results = set.cartprod([[]]).to_a
+    set     = subject[1,2]
+    results = set.cartprod([2,3],[]).to_a
 
     results.should be_empty
   end
@@ -49,21 +49,21 @@
     set     = subject[1, 2]
     results = set.cartprod([3, 4]).to_a
 
-    results.should =~ [[1, 3], [1, 4], [2, 3], [2, 4]]
+    results.should =~ [
+      [1, 3], [1, 4],
+      [2, 3], [2, 4]
+    ]
   end
 
   it "the cartprod of [0, 1] and [[2, 3], [4, 5]] should be [[0, 2, 4], [1, 2, 4], [0, 3, 4], [1, 3, 4], [0, 2, 5], [1, 2, 5], [0, 3, 5], [1, 3, 5]]" do
     set1    = subject[0, 1]
     set2    = subject[2, 3]
     set3    = subject[4, 5]
-    results = set1.cartprod([set2, set3]).to_a
+    results = set1.cartprod(set2, set3).to_a
 
     results.should =~ [
-      [0, 2, 4],
-      [1, 2, 4],
-      [0, 3, 4],
-      [1, 3, 4],
-      [0, 2, 5]
+      [0, 2, 4], [0, 2, 5], [0, 3, 4], [0, 3, 5],
+      [1, 2, 4], [1, 2, 5], [1, 3, 4], [1, 3, 5],
     ]
   end