5yku 难度
Ruby has very powerful enumerator support, including the ability to create your own custom enumerators on the fly.
digits = Enumerator.new do |y|
i = 0
loop do
y.yield i
i += 1
end
end
digits.next # => 0
digits.next # => 1
digits.take_while {|n| n < 13} # => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
Create an enumerator "fib" that outputs successive fibonacci numbers.
For example:
fib.next # => 1
fib.next # => 1
fib.next # => 2
fib.take_while {|n| n < 100} # => [1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89]
fib = Enumerator.new do |y|
i, j = 1, 1
loop do
y.yield i
i, j = j, i + j
end
end
