From: Farrel Lifson <farrel.lifson@...>
Date: 2006-11-15T15:59:52+09:00
Subject: Re: Design problem with 'inject'

On 15/11/06, Marcel Molina Jr. <marcel@vernix.org> wrote:
> On Wed, Nov 15, 2006 at 03:46:44PM +0900, Gary Boone wrote:
> > Ruby's inject has a design that can lead to hard to find bugs. The
> > problem is that you don't have to specify what is summed; the value of
> > the block is summed. That means 'next' can lead to a bug. Here's an
> > example:
> >
> > No problem:
> >
> >    arr.inject(0) do |sum, i|
> >                     sum += i
> >                  done
> >
> > But suppose you need to skip some elements, so you add a 'next'
> > statement.
> > Problem:
> >
> >    arr.inject(0) do |sum, i|
> >                    next if (i==3)
> >                    sum += i
> >                  done
>
> You need to do this:
>
>   next sum if i == 3
>
> Also:
>
>   sum += 1
>
> This unecessarily modifies the sum.
>
>   sum + 1
>
> Will suffice.
>
> marcel
> --
> Marcel Molina Jr. <marcel@vernix.org>

Whoa! That is good to know.

Farrel