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require 'spec_helper'
describe Immutable::Vector do
describe '#product' do
context 'when passed no arguments' do
it 'multiplies all items in vector' do
[
[[], 1],
[[2], 2],
[[1, 3, 5, 7, 11], 1155],
].each do |values, expected|
V[*values].product.should == expected
end
end
end
context 'when passed one or more vectors' do
let(:vector) { V[1,2,3] }
context 'when passed a block' do
it 'yields an array for each combination of items from the vectors' do
yielded = []
vector.product(vector) { |obj| yielded << obj }
yielded.should eql([[1,1], [1,2], [1,3], [2,1], [2,2], [2,3], [3,1], [3,2], [3,3]])
yielded = []
vector.product(V[3,4,5], V[6,8]) { |obj| yielded << obj }
yielded.should eql(
[[1, 3, 6], [1, 3, 8], [1, 4, 6], [1, 4, 8], [1, 5, 6], [1, 5, 8],
[2, 3, 6], [2, 3, 8], [2, 4, 6], [2, 4, 8], [2, 5, 6], [2, 5, 8],
[3, 3, 6], [3, 3, 8], [3, 4, 6], [3, 4, 8], [3, 5, 6], [3, 5, 8]])
end
it 'returns self' do
vector.product(V.empty) {}.should be(vector)
vector.product(V[1,2], V[3]) {}.should be(vector)
V.empty.product(vector) {}.should be(V.empty)
end
end
context 'when not passed a block' do
it 'returns the cartesian product in an array' do
V[1,2].product(V[3,4,5], V[6,8]).should eql(
[[1, 3, 6], [1, 3, 8], [1, 4, 6], [1, 4, 8], [1, 5, 6], [1, 5, 8],
[2, 3, 6], [2, 3, 8], [2, 4, 6], [2, 4, 8], [2, 5, 6], [2, 5, 8]])
end
end
context 'when one of the arguments is empty' do
it 'returns an empty array' do
vector.product(V.empty, V[4,5,6]).should eql([])
end
end
context 'when the receiver is empty' do
it 'returns an empty array' do
V.empty.product(vector, V[4,5,6]).should eql([])
end
end
end
context 'when passed one or more Arrays' do
it 'also calculates the cartesian product correctly' do
V[1,2].product([3,4,5], [6,8]).should eql(
[[1, 3, 6], [1, 3, 8], [1, 4, 6], [1, 4, 8], [1, 5, 6], [1, 5, 8],
[2, 3, 6], [2, 3, 8], [2, 4, 6], [2, 4, 8], [2, 5, 6], [2, 5, 8]])
end
end
end
end
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