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require 'spec_helper'
describe Immutable::List do
describe '#combination' do
it 'is lazy' do
-> { Immutable.stream { fail }.combination(2) }.should_not raise_error
end
[
[%w[A B C D], 1, [L['A'], L['B'], L['C'], L['D']]],
[%w[A B C D], 2, [L['A','B'], L['A','C'], L['A','D'], L['B','C'], L['B','D'], L['C','D']]],
[%w[A B C D], 3, [L['A','B','C'], L['A','B','D'], L['A','C','D'], L['B','C','D']]],
[%w[A B C D], 4, [L['A', 'B', 'C', 'D']]],
[%w[A B C D], 0, [EmptyList]],
[%w[A B C D], 5, []],
[[], 0, [EmptyList]],
[[], 1, []],
].each do |values, number, expected|
context "on #{values.inspect} in groups of #{number}" do
let(:list) { L[*values] }
it 'preserves the original' do
list.combination(number)
list.should eql(L[*values])
end
it "returns #{expected.inspect}" do
list.combination(number).should eql(L[*expected])
end
end
end
end
end
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