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Contents
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 RuntimeError
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
13 entries across 13 versions & 1 rubygems