From: "David A. Black" <dblack@...>
Date: 2004-03-19T23:58:42+09:00
Subject: Re: Can I stop each's iteration, and get the results so far?

Hi --

On Fri, 19 Mar 2004, Sam Roberts wrote:

> Wrote Robert Klemme <bob.news@gmx.net>, on Fri, Mar 19, 2004 at 05:59:36PM +0900:
> > > Basically, I want to break from a find_all, and get the array of
> > > elements found so far. Is this possible?
> > >
> > > I tried this, no luck with find_all and collect, they return nil,
> > > instead of the array so far. Any suggestions on how to do this?
> > 
> > #inject is your friend:
> > 
> > > puts "all n between 100 and 200?"
> > >
> > > p every.find_all { |n| break if n > 200; n >= 100 && n <= 200 }
> > 
> > irb(main):076:0> every.inject([]) { |arr,n| break arr if n > 200; arr<<n
> > if n >= 100 && n <= 200; arr }
> > => [102, 105, 108, 111, 114, 117, 120, 123, 126, 129, 132, 135, 138, 141,
> > 144, 147, 150, 153, 156, 159, 162, 165, 168, 171, 174, 177, 180, 183, 186,
> > 189, 192, 195, 198]
> 
> Thanks, thats useful to know, and odd!
> 
> Why can you break from inject and get the result, but not from find_all
> or collect?
> 
> Is this a bug, an oversight, or is something about the methods that
> makes them need to be different?

I think the idea of breaking from find_all is sort of contradictory,
since it runs counter to the "all" part of "find_all" :-)

But anyway... what Robert does is "break arr" -- that is, he gives
break an argument.  That argument then becomes the return value of the
whole thing.  You can't do that with find_all, because you don't have
direct access to the accumulator ("arr" in Robert's example).


David

-- 
David A. Black
dblack@wobblini.net