From: Eric Mahurin <eric.mahurin@...>
Date: 2005-10-31T09:34:51+09:00
Subject: Re: Very useful... 'break' accepts an argument

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On 10/30/05, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
>
> Tom Agnew wrote:
> > Greetings,
> >
> > I just discovered undocumented but very useful syntax:
> >
> > break <expression>
> >
> > The expression seems to add a useful feature to a 'while', 'until' or
> > 'for' control structure. For example:
> >
> > result =3D while <condition>
> > ...
> > break <something>
> > ...
> > end
> >
> > 'result' is nil if the loop exits with <condition> and is <something> i=
f
> > the break is executed.
> >
> > Very useful and provides an cool addition to an already elegant
> > collection of iterator constructs!
> >
> > Tom Agnew3
> >
>
> It's also cool because it works with your own iterators (really, any
> method that takes a block), not just ruby syntax like while.
>
> def foo
> yield
> end
>
> x =3D foo do
> break 4
> end
>
> p x
>

Unfortunately the base iterators return the object they are iterating over
instead of nil like the non-iterator loops (while, until, loop). For the
non-iterator loops nil can mean terminate normally if you use break with a
value (non-nil). For iterator loops you have to do the opposite - break wit=
h
a value is of little use.

I discussed the problem here:

http://rcrchive.net/rcr/show/305

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