* lib/matrix.rb: Allow non integer exponents for Matrix#**

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32352 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

3 files changed, 11 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index d0d58082cc..a5c3ba9a00 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Jul  1 15:21:14 2011  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
+
+	* lib/matrix.rb: Allow non integer exponents for Matrix#**
+
 Fri Jul  1 15:13:25 2011  Marc-Andre Lafortune  <ruby-core@marc-andre.ca>
 
 	* lib/matrix: Add Eigenvalue Decomposition
diff --git a/NEWS b/NEWS
index dd6ab19623..cee2bc0777 100644
--- a/NEWS
+++ b/NEWS
@@ -178,6 +178,7 @@ with all sufficient information, see the ChangeLog file.
     * Matrix#each and #each_with_index can iterate on a subset of the elements
     * Matrix#find_index returns [row, column] and can iterate on a subset
       of the elements
+    * Matrix#** implements Numeric exponents (using the eigensystem)
     * Matrix.zero can build rectangular matrices
 
 * net/http
diff --git a/lib/matrix.rb b/lib/matrix.rb
index 8c6b3d6e87..5ce130221f 100644
--- a/lib/matrix.rb
+++ b/lib/matrix.rb
@@ -956,8 +956,10 @@ class Matrix
   private :inverse_from
 
   #
-  # Matrix exponentiation.  Currently implemented for integer powers only.
+  # Matrix exponentiation.
   # Equivalent to multiplying the matrix by itself N times.
+  # Non integer exponents will be handled by diagonalizing the matrix.
+  #
   #   Matrix[[7,6], [3,9]] ** 2
   #     => 67 96
   #        48 99
@@ -977,8 +979,9 @@ class Matrix
         return z if (other >>= 1).zero?
         x *= x
       end
-    when Float, Rational
-      Matrix.Raise ErrOperationNotImplemented, "**", self.class, other.class
+    when Numeric
+      v, d, v_inv = eigensystem
+      v * Matrix.diagonal(*d.each(:diagonal).map{|e| e ** other}) * v_inv
     else
       Matrix.Raise ErrOperationNotDefined, "**", self.class, other.class
     end