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1d15d5f080
* Other ruby implementations use the spec/ruby directory. [Misc #13792] [ruby-core:82287] git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59979 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
74 lines
2.3 KiB
Ruby
74 lines
2.3 KiB
Ruby
require File.expand_path('../../../spec_helper', __FILE__)
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describe "Array#combination" do
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before :each do
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@array = [1, 2, 3, 4]
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end
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it "returns an enumerator when no block is provided" do
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@array.combination(2).should be_an_instance_of(Enumerator)
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end
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it "returns self when a block is given" do
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@array.combination(2){}.should equal(@array)
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end
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it "yields nothing for out of bounds length and return self" do
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@array.combination(5).to_a.should == []
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@array.combination(-1).to_a.should == []
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end
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it "yields the expected combinations" do
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@array.combination(3).to_a.sort.should == [[1,2,3],[1,2,4],[1,3,4],[2,3,4]]
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end
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it "yields nothing if the argument is out of bounds" do
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@array.combination(-1).to_a.should == []
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@array.combination(5).to_a.should == []
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end
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it "yields a copy of self if the argument is the size of the receiver" do
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r = @array.combination(4).to_a
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r.should == [@array]
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r[0].should_not equal(@array)
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end
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it "yields [] when length is 0" do
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@array.combination(0).to_a.should == [[]] # one combination of length 0
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[].combination(0).to_a.should == [[]] # one combination of length 0
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end
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it "yields a partition consisting of only singletons" do
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@array.combination(1).to_a.sort.should == [[1],[2],[3],[4]]
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end
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it "generates from a defensive copy, ignoring mutations" do
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accum = []
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@array.combination(2) do |x|
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accum << x
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@array[0] = 1
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end
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accum.should == [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]
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end
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describe "when no block is given" do
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describe "returned Enumerator" do
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describe "size" do
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it "returns 0 when the number of combinations is < 0" do
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@array.combination(-1).size.should == 0
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[].combination(-2).size.should == 0
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end
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it "returns the binomial coeficient between the array size the number of combinations" do
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@array.combination(5).size.should == 0
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@array.combination(4).size.should == 1
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@array.combination(3).size.should == 4
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@array.combination(2).size.should == 6
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@array.combination(1).size.should == 4
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@array.combination(0).size.should == 1
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[].combination(0).size.should == 1
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[].combination(1).size.should == 0
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end
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end
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end
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end
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end
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