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| class Array | |
| def skip_first?(accumulator) | |
| return 1 if accumulator.nil? | |
| return 0 unless accumulator.nil? | |
| end | |
| def my_inject(accumulator = nil) | |
| start = skip_first? accumulator | |
| accumulator ||= self.first | |
| if block_given? | |
| self[start..-1].each do |number| | |
| accumulator = yield(accumulator,number) | |
| end | |
| end | |
| accumulator | |
| end | |
| end | |
| describe "my inject method" do | |
| context 'when there is less than two elements with no initial accumulator' do | |
| it "empty array be nil" do | |
| expect([].my_inject).to eq [].inject | |
| end | |
| it "single array should return it's element" do | |
| expect([0].my_inject).to eq [0].inject | |
| end | |
| end | |
| context 'where there is 3 or more elements with no initial accumulator' do | |
| it "uses the first element as the seed" do | |
| sum = lambda {|sum,number| sum + number } | |
| expect([1,2,3].my_inject &sum).to eq [1,2,3].inject &sum | |
| end | |
| end | |
| context 'where there is 2 or more elements with an initial accumulator' do | |
| it "uses the first element as the seed" do | |
| result = [1,2,3].my_inject(100) {|sum,number| sum + number } | |
| expected = [1,2,3].inject(100) {|sum,number| sum + number } | |
| expect(result).to eq expected | |
| end | |
| end | |
| end |
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