* lib/matrix.rb: Add Vector#cross_product, patch by Luis Ezcurdia

[fix GH-276] [rubyspec:81eec89a124]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40273 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Sat Apr 13 12:08:16 2013  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
+
+	* lib/matrix.rb: Add Vector#cross_product, patch by Luis Ezcurdia
+	  [fix GH-276] [rubyspec:81eec89a124]
+
 Sat Apr 13 10:20:37 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* struct.c (rb_struct_define_without_accessor, rb_struct_define),

NEWS

@@ -38,6 +38,9 @@ with all sufficient information, see the ChangeLog file.
 
 === Stdlib updates (outstanding ones only)
 
+* Matrix
+  * Added Vector#cross_product.
+
 * Net::SMTP
   * Added Net::SMTP#rset to implement the RSET command
 

lib/matrix.rb

@@ -1519,6 +1519,7 @@ end
 #
 # Vector functions:
 # * #inner_product(v)
+# * #cross_product(v)
 # * #collect
 # * #magnitude
 # * #map
@@ -1757,6 +1758,17 @@ class Vector
     p
   end
 
+  #
+  # Returns the cross product of this vector whit the other.
+  #   Vector[1, 0, 0].cross_product Vector[0, 1, 0]   => Vector[0, 0, 1]
+  #
+  def cross_product(v)
+    Vector.Raise ErrDimensionMismatch unless size == v.size && v.size == 3
+    Vector[ v[1]*@elements[2] - v[2]*@elements[1],
+            v[2]*@elements[0] - v[0]*@elements[2],
+            v[0]*@elements[1] - v[1]*@elements[0] ]
+  end
+
   #
   # Like Array#collect.
   #