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require 'matrix'
describe :determinant, :shared => true do
# Ruby versions less than 1.9.0, AFAICT, return the wrong determinant in
# most non-trivial cases. As the rdoc for Matrix suggests, "require 'mathn'"
# seems to fix this, but as Matrix doesn't require that library itself, the
# bug remains. I've reported http://redmine.ruby-lang.org/issues/show/1516 ,
# which is ostensibly about the documentation for #determinant not
# reflecting this bug, but raises the question of why 1.8.7 doesn't handle
# this properly.
ruby_bug "#1516", "1.8.7" do
it "returns the determinant of a square Matrix" do
m = Matrix[ [7,6], [3,9] ]
m.send(@method).should == 45
m = Matrix[ [9, 8], [6,5] ]
m.send(@method).should == -3
m = Matrix[ [9,8,3], [4,20,5], [1,1,1] ]
m.send(@method).should == 95
end
end
it "returns the determinant of a single-element Matrix" do
m = Matrix[ [2] ]
m.send(@method).should == 2
end
ruby_bug "redmine:1532", "1.8.7" do
it "returns 1 for an empty Matrix" do
m = Matrix[ ]
m.send(@method).should == 1
end
end
ruby_bug "#1531", "1.8.7" do
it "returns the determinant even for Matrices containing 0 as first entry" do
Matrix[[0,1],[1,0]].send(@method).should == -1
end
end
ruby_bug "#2770", "1.8.7" do
it "raises an error for rectangular matrices" do
lambda {
Matrix[[1], [2], [3]].send(@method)
}.should raise_error(Matrix::ErrDimensionMismatch)
lambda {
Matrix.empty(3,0).send(@method)
}.should raise_error(Matrix::ErrDimensionMismatch)
end
end
end
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