From: Matthew Smillie <M.B.Smillie@...>
Date: 2006-11-15T19:09:34+09:00
Subject: Re: Design problem with 'inject'

On Nov 15, 2006, at 8:51, Gary Boone wrote:

>
> Those are several good suggestions.
>
>    next sum if (i == 3)
>
> strikes me as simple and clear. Provided you know that the block  
> result
> is what matters, you can stay out of trouble.
>
> Simplifying the example, the trouble with inject is that
>
>    arr.inject(0) { |sum, i| sum += i }
>    arr.inject(0) { |sum, i| sum + i }
>
> both produce the same result. Yuk.
>
> Maybe it should be posted somewhere as a potential 'gotcha'.

I think it could be that I'm just too familiar with the whole  
accumulator thing, but I'm having trouble even imagining a case where  
you'd want it any other way.  Why would you want those to produce  
different results, and - here I can't even guess - what would those  
different results actually be?

I have a hunch that the key phrase is "Provided you know that the  
block result is what matters, you can stay out of trouble."  I mean,  
that's sort of inherent in the construct.  If you don't know that,  
I'd you're going to have a lot of trouble with #inject.

m.s.