From: timr <timrandg@...>
Date: 2010-08-28T14:15:06+09:00
Subject: Re: how about Array#collect_until


> I know you already got something that works, but I think this is a
> problem where enumerators provide an elegant solution:
>
> module Enumerable
>   def through
>     Enumerator.new do |yielder|
>       self.each do |val|
>         yielder.yield(val)
>         break if yield val
>       end
>     end
>   end
> end
>
> then:
>
> [1,2,3].through {|x| x % 2 == 0}.collect {|item| item+10} => [11,12]

Thanks for another useful answer.

I need to read the doc for Enumerator class since I don't really know
how to use it, but your solution appears to run each item into the
first block, until it finds an item producing a true result and then
everything up to that point is sent on to a collect statement for
processing in the second block. I am sure this is going to be useful
in many cases, but it is different from what I was intending for the
collect_until function. You will see how our two solutions differ if
you look at the test cases and the results below.

%w[ find out if that  this  but not the other mother
mouth].collect_until(lambda {|word| word[-2,2] == 'st' }){|item| item
+ "t" } # => ["findt", "outt", "ift", "thatt", "thist"]

[1,6,7,5,3,0,10,12,14].collect_until(Proc.new {|num| num > 25 }){|
item| item * 4 } # => [4, 24, 28]

[1,2,3].collect_until(Proc.new {|x| x%2 == 0}) {|item| item + 10} # =>
[11, 12]


Versus:
%w[ find out if that  this  but not the other mother mouth].through {|
word| word[-2,2] == 'st' }.collect{|item| item + "t" } # => ["findt",
"outt", "ift", "thatt", "thist", "butt", "nott", "thet", "othert",
"mothert", "moutht"]

[1,6,7,5,3,0,10,12,14].through {|num| num > 25 }.collect{|item| item *
4 } # => [4, 24, 28, 20, 12, 0, 40, 48, 56]

[1,2,3].through {|x| x%2 == 0}.collect{|item| item + 10} # => [11, 12]