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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
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stomar committed Jan 11, 2018
1 parent 9e67726 commit 3b51e3a11fd39daafaaaf54bcbf81814d48c3942
Showing with 47 additions and 0 deletions.
  1. +12 −0 lib/matrix.rb
  2. +35 −0 spec/ruby/library/matrix/antisymmetric_spec.rb
@@ -801,6 +801,18 @@ def symmetric?
true
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.
@@ -0,0 +1,35 @@
require File.expand_path('../../../spec_helper', __FILE__)
require 'matrix'
describe "Matrix#antisymmetric?" do
it "returns true for an antisymmetric Matrix" do
Matrix[[0, -2, Complex(1, 3)], [2, 0, 5], [-Complex(1, 3), -5, 0]].antisymmetric?.should be_true
end
it "returns true for a 0x0 empty matrix" do
Matrix.empty.antisymmetric?.should be_true
end
it "returns false for non-antisymmetric matrices" do
[
Matrix[[1, 2, 3], [4, 5, 6], [7, 8, 9]],
Matrix[[1, -2, 3], [2, 0, 6], [-3, -6, 0]], # wrong diagonal element
Matrix[[0, 2, -3], [2, 0, 6], [-3, 6, 0]] # only signs wrong
].each do |matrix|
matrix.antisymmetric?.should be_false
end
end
it "raises an error for rectangular matrices" do
[
Matrix[[0], [0]],
Matrix[[0, 0]],
Matrix.empty(0, 2),
Matrix.empty(2, 0),
].each do |rectangular_matrix|
lambda {
rectangular_matrix.antisymmetric?
}.should raise_error(Matrix::ErrDimensionMismatch)
end
end
end

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