From: Robert Klemme <shortcutter@...>
Date: 2011-03-25T16:48:34+09:00
Subject: Re: break from select

On Fri, Mar 25, 2011 at 8:37 AM, Saravanan Krishnan
<saravani20@gmail.com> wrote:
> Hi venkat,
>
> Here is the better solution,
>
> a = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
> b = []
> a.each do |x|
>  next if b.length >= 5
>  b << x if x % 2 ==0
> end
>
> puts b

You are still iterating the whole input Array.  This is better

irb(main):001:0> a = 1.upto(15).to_a
=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
irb(main):002:0> b = []
=> []
irb(main):003:0> a.each {|x| if x % 2 == 0; b << x; break if b.size >= 5 end}
=> nil
irb(main):004:0> b
=> [2, 4, 6, 8, 10]

Insert "p x" at beginning of block to see that we really short circuit.

If you want to get fancy you can do this as well:

irb(main):010:0> b = []
=> []
irb(main):011:0> a.each {|x| p x; x % 2 == 0 and b << x and b.size >=
5 and break}
1
2
3
4
5
6
7
8
9
10
=> nil

We can even integrate this with #inject to get a *cough* one liner:

irb(main):012:0> b = a.inject([]) {|c,x| p x; x % 2 == 0 and c << x
and c.size >= 5 and break c or c}
1
2
3
4
5
6
7
8
9
10
=> [2, 4, 6, 8, 10]

:-)

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/