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require 'rspec' require 'abstractivator/enumerator_ext' describe 'Enumerator' do describe '::unfold' do it 'generates an enumerator based on state changes over time' do naturals = Enumerator.unfold(1) { |nxt| [nxt, nxt + 1] } expect(naturals.take(5)).to eql [1,2,3,4,5] end it 'stops when state becomes nil' do xs = [1,2,3] tails = Enumerator.unfold(xs) { |xs| xs.empty? ? [nil, nil] : [xs, xs.drop(1)] } expect(tails.to_a).to eql [[1,2,3],[2,3],[3]] end it 'returns an empty array if the initial state is nil' do expect(Enumerator.unfold(nil){}.to_a).to eql [] end it 'raises an error if no block is provided' do expect{Enumerator.unfold(nil)}.to raise_error end end describe '#memoized' do it 'returns a memoized version of the enumerator' do work = [] naturals = Enumerator.new do |y| i = 1 loop do # puts "calculating #{i}" work << i y << i i += 1 end end wrapped = naturals.memoized expect(wrapped.take(3)).to eql [1,2,3] expect(work).to eql [1,2,3] # reenumerating doesn't do additional work expect(wrapped.take(3)).to eql [1,2,3] expect(work).to eql [1,2,3] # enumerating more does the minimum amount of work expect(wrapped.take(5)).to eql [1,2,3,4,5] expect(work).to eql [1,2,3,4,5] # subsequent calls share the memo wrapped2 = naturals.memoized expect(wrapped2.take(5)).to eql [1,2,3,4,5] expect(work).to eql [1,2,3,4,5] # wrapped instances are independent a = naturals.memoized b = naturals.memoized expect(a.next).to eql 1 expect(a.next).to eql 2 expect(b.next).to eql 1 expect(a.next).to eql 3 expect(b.next).to eql 2 # wrapped enumerator is unaffected expect(naturals.next).to eql 1 expect(naturals.take(3)).to eql [1,2,3] end end end
Version data entries
4 entries across 4 versions & 1 rubygems