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require "spec_helper"
require "hamster/vector"
describe Hamster::Vector do
describe "#permutation" do
let(:vector) { V[1,2,3,4] }
context "without a block or arguments" do
it "returns an Enumerator of all permutations" do
vector.permutation.class.should be(Enumerator)
vector.permutation.to_a.should eql(vector.to_a.permutation.to_a)
end
end
context "without a block, but with integral argument" do
it "returns an Enumerator of all permutations of given length" do
vector.permutation(2).class.should be(Enumerator)
vector.permutation(2).to_a.should eql(vector.to_a.permutation(2).to_a)
vector.permutation(3).class.should be(Enumerator)
vector.permutation(3).to_a.should eql(vector.to_a.permutation(3).to_a)
end
end
context "with a block" do
it "returns self" do
vector.permutation {}.should be(vector)
end
context "and no argument" do
it "yields all permutations" do
yielded = []
vector.permutation { |obj| yielded << obj }
yielded.sort.should eql([[1,2,3,4], [1,2,4,3], [1,3,2,4], [1,3,4,2],
[1,4,2,3], [1,4,3,2], [2,1,3,4], [2,1,4,3], [2,3,1,4], [2,3,4,1],
[2,4,1,3], [2,4,3,1], [3,1,2,4], [3,1,4,2], [3,2,1,4], [3,2,4,1],
[3,4,1,2], [3,4,2,1], [4,1,2,3], [4,1,3,2], [4,2,1,3], [4,2,3,1],
[4,3,1,2], [4,3,2,1]])
end
end
context "and an integral argument" do
it "yields all permutations of the given length" do
yielded = []
vector.permutation(2) { |obj| yielded << obj }
yielded.sort.should eql([[1,2], [1,3], [1,4], [2,1], [2,3], [2,4], [3,1],
[3,2], [3,4], [4,1], [4,2], [4,3]])
end
end
end
context "on an empty vector" do
it "yields the empty permutation" do
yielded = []
V.empty.permutation { |obj| yielded << obj }
yielded.should eql([[]])
end
end
context "with an argument of zero" do
it "yields the empty permutation" do
yielded = []
vector.permutation(0) { |obj| yielded << obj }
yielded.should eql([[]])
end
end
context "with a length greater than the size of the vector" do
it "yields no permutations" do
vector.permutation(5) { |obj| fail }
end
end
it "handles duplicate elements correctly" do
V[1,2,3,1].permutation(2).sort.should eql([[1,1], [1,1], [1,2], [1,2],
[1,3], [1,3], [2,1],[2,1],[2,3], [3,1],[3,1],[3,2]])
end
it "leaves the original unmodified" do
vector.permutation(2) {}
vector.should eql(V[1,2,3,4])
end
it "behaves like Array#permutation" do
10.times do
array = rand(8).times.map { rand(10000) }
vector = V.new(array)
perm_size = array.size == 0 ? 0 : rand(array.size)
array.permutation(perm_size).to_a.should == vector.permutation(perm_size).to_a
end
end
end
end
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