Stream是一种能容纳无穷对象的容器,我在研究了Js的实现后,尝试用Ruby实现一下。另外加上阶乘数列和 费波纳茨数列的实现。
Stream.js的介绍: http://www.aqee.net/stream-javascript-lib/
Stream的详情请参考: http://www.aqee.net/docs/stream/
class Stream
def initialize(head = nil, tail = nil)
@head = head
@tailFunc = tail
end
def empty?
@head == nil
end
def head
@head
end
def tail
@tailFunc.call
end
def length
count = 0
walk { count += 1}
return count
end
def add(s2)
return zip(s2) {|x, y| x + y}
end
def substract(s2)
return zip(s2) {|x, y| x - y}
end
def times(s2)
return zip(s2) {|x, y| x * y}
end
def zip(s2, &block)
return s2 if empty?
return self if s2.empty?
return Stream.new(block.call(head, s2.head), lambda { tail.zip(s2.tail, &block) })
end
def take(count)
return self if empty?
return Stream.new if count == 0
return Stream.new(head, lambda { tail.take(count - 1) })
end
def map(&block)
return self if empty?
return Stream.new(block.call(head), lambda { tail.map(&block) })
end
def scale(factor)
return map { |x| x * factor}
end
def filter(&block)
return self if empty?
return Stream.new(head, lambda { tail.filter(&block) }) if block.call(head)
return tail.filter(&block)
end
def drop(count)
return self if empty?
s = self
count.times {s = s.tail}
return s
end
def member?(item)
s = self
s = s.tail until s.empty? || s.head == item
return s.head == item
end
def force
s = self
s = s.tail until (s.empty?)
end
def walk(&block)
map { |s| block.call(s); s }.force
end
def print
walk { |s| puts s}
end
def item(index)
s = self
index.times { s = s.tail}
return s.head
end
def sum
return reduce(0) {|sum, new| sum + new}
end
def reduce(init, &block)
return init if empty?
return tail.reduce(block.call(init, head), &block);
end
def Stream.range(low = 1, high = nil)
return Stream.make(low) if low == high
return Stream.new(low, lambda { Stream.range(low + 1, high) })
end
def Stream.make(*args)
return Stream.new if args.empty?
return Stream.new(args.shift, lambda { Stream.make(*args) })
end
def Stream.make_ones
return Stream.new(1, lambda { Stream.make_ones })
end
def Stream.make_natural_nums
return Stream.new(1, lambda{ Stream.make_ones.add(Stream.make_natural_nums) })
end
def Stream.make_fib_nums_drop1
return Stream.new(1, lambda {Stream.make_fib_nums.add(Stream.make_fib_nums_drop1) })
end
def Stream.make_fib_nums
return Stream.new(0, lambda { Stream.make_fib_nums_drop1 })
end
def Stream.make_factor
return Stream.new(1, lambda { Stream.make_natural_nums.drop(1).times(Stream.make_factor) })
end
end
Stream.make_factor.take(10).print