1 files changed, 51 insertions, 0 deletions
diff --git a/spec/ruby/library/matrix/exponent_spec.rb b/spec/ruby/library/matrix/exponent_spec.rb
new file mode 100644
index 0000000000..188a1b34d2
--- /dev/null
+++ b/spec/ruby/library/matrix/exponent_spec.rb
@@ -0,0 +1,51 @@
+require File.expand_path('../../../spec_helper', __FILE__)
+require File.expand_path('../fixtures/classes', __FILE__)
+require 'matrix'
+
+describe "Matrix#**" do
+
+  describe "given an integer _n_" do
+    it "multiples the Matrix by itself _n_ times" do
+      m = Matrix[ [7,6], [3,9] ]
+      (m ** 1).should == m
+      (m ** 2).should == Matrix[ [67, 96], [48,99] ]
+      (m ** 2).should == m * m
+      (m ** 3).should == m * m * m
+      (m ** 4).should == m * m * m * m
+      (m ** 5).should == m * m * m * m * m
+    end
+
+    it "raises a ErrDimensionMismatch for non square matrices" do
+      m = Matrix[ [1, 1], [1, 2], [2, 3]]
+      lambda { m ** 3 }.should raise_error(Matrix::ErrDimensionMismatch)
+      lambda { m ** 0 }.should raise_error(Matrix::ErrDimensionMismatch)
+    end
+
+    describe "that is <= 0" do
+      it "returns the inverse of **(-n)" do
+        m = Matrix[ [1, 1], [1, 2] ]
+        (m ** -2).should == Matrix[ [5, -3], [-3, 2]]
+        (m ** -4).should == (m.inverse ** 4)
+      end
+
+      it "raises a ErrDimensionMismatch for irregular matrices" do
+        m = Matrix[ [1, 1], [1, 1] ]
+        lambda { m ** -2 }.should raise_error(Matrix::ErrNotRegular)
+        lambda { m ** 0 }.should raise_error(Matrix::ErrNotRegular)
+      end
+    end
+  end
+
+  it "returns the power for non integer powers" do
+    a = Matrix[[5, 4], [4, 5]]
+    ((a ** 0.5) ** 2).round(8).should == a
+    a = Matrix[[7, 10], [15, 22]]
+    ((a ** 0.25) ** 4).round(8).should == a
+  end
+
+  describe "for a subclass of Matrix" do
+    it "returns an instance of that subclass" do
+      (MatrixSub.ins ** 1).should be_an_instance_of(MatrixSub)
+    end
+  end
+end