matrix.rb: add Matrix#antisymmetric?

* lib/matrix.rb: add Matrix#antisymmetric?.
  Proposed by Yilo (@yiloo). Patch by Marcus Stollsteimer (@stomar).
  [Fix GH-1788]
* spec/ruby/library/matrix/antisymmetric_spec.rb: add specs.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61775 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/matrix.rb b/lib/matrix.rb
index 923e716b35..4a61976b0e 100644
--- a/lib/matrix.rb
+++ b/lib/matrix.rb
@@ -802,6 +802,18 @@ class Matrix
   end
 
   #
+  # Returns +true+ if this is an antisymmetric matrix.
+  # Raises an error if matrix is not square.
+  #
+  def antisymmetric?
+    Matrix.Raise ErrDimensionMismatch unless square?
+    each_with_index(:upper) do |e, row, col|
+      return false unless e == -rows[col][row]
+    end
+    true
+  end
+
+  #
   # Returns +true+ if this is a unitary matrix
   # Raises an error if matrix is not square.
   #