Enumerating lazily

wtd · **Posted:** Sun Jan 31, 2010 11:47 pm

Ruby:

class X
def initialize(obj)
@obj = obj
   @calls = []
end

def collect(&block)
   @calls.push([:collect, block])
   self
end

def each(&block)
   @calls.push([:each, block])

@obj.each do |x|
   @calls.each do |c|
   r = c[1].call(x)

x = r if c[0] == :collect
   end
   end

   @calls = []
end
end

module Enumerable
def lazy
   X.new(self)
end
end

[1, 2, 3].lazy.collect { |x|
x * 2
}.collect { |x|
x + 1
}.each { |x|
puts x
break if x > 4
}

wtd · **Posted:** Mon Feb 01, 2010 12:31 am

code:

>> [1, 2, 3].lazy.collect { |x|
?> puts "loop one #{x}"
>> x * 2
>> }.collect { |x|
?> puts "loop two #{x}"
>> x + 1
>> }.each { |x|
?> puts x
>> break if x > 4
>> }
loop one 1
loop two 2
3
loop one 2
loop two 4
5
=> nil

code:

>> [1, 2, 3].collect { |x|
?> puts "loop one #{x}"
>> x * 2
>> }.collect { |x|
?> puts "loop two #{x}"
>> x + 1
>> }.each { |x|
?> puts x
>> break if x > 4
>> }
loop one 1
loop one 2
loop one 3
loop two 2
loop two 4
loop two 6
3
5
=> nil

	Computer Science Canada Programming C, C++, Java, PHP, Ruby, Turing, VB Username: Password: Register
Wiki Blog Search Turing Chat Room Members