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Feature #707 » fib.rb

candlerb (Brian Candler), 11/03/2008 06:41 PM

 
class Enumerator
def lazy_map(&blk)
Enumerator.new do |y|
each do |e|
y << blk[e]
end
end
end

def lazy_select(&blk)
Enumerator.new do |y|
each do |e|
y << e if blk[e]
end
end
end
end

class Fib
def initialize(a=1,b=1)
@a, @b = a, b
end
def each
a, b = @a, @b
yield a
while true
yield b
a, b = b, a+b
end
end
end

Fib.new.to_enum. # generator
lazy_select { |x| x % 2 == 0 }. # filter
lazy_map { |x| "<#{x}>" }. # filter
each_with_index { |x,c| puts x; break if c >= 20 } # consumer
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