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comp.lang.ruby

Re: "Pointer" to an object? (i.e. reflect changes to origina

Brian Candler

9/9/2008 12:52:00 PM

> Both lambda and proc work
> as well, incidentally. Actually, from what I've read they're identical
> in 1.8 (which is what I'm using), but not in 1.9,

Not exactly.

* lambda and Proc are different to each other in both ruby1.8 and ruby1.9.
Also, they are different in the same way :-)

* in ruby1.8, proc {} is a synonym for lambda {}

* in ruby1.9, proc {} is a synonym for Proc.new {}

So to play it safe, never use proc {} - always use lambda {} or Proc.new {}

For a detailled discussion of the differences, see
http://innig.net/software/ruby/closures-...

(although I disagree with his rant: these inconsistencies are carefully
considered to make Ruby "do the right thing" in various scenarios)

If you are using closures in the way discussed in this thread, then I think
lambda {} is probably the best choice as you get a true closure which is
fully independent of the thread of execution where it was defined.

Regards,

Brian.
1 Answer

David A. Black

9/9/2008 1:11:00 PM

0

Hi Brian --

On Tue, 9 Sep 2008, Brian Candler wrote:

>> Both lambda and proc work
>> as well, incidentally. Actually, from what I've read they're identical
>> in 1.8 (which is what I'm using), but not in 1.9,
>
> Not exactly.

I think the statement as written is correct: lambda and proc are the
same in 1.8 (with Proc.new being different from both), but in 1.9,
lambda is one thing and proc/Proc.new are another (and the same as
each other).

> * lambda and Proc are different to each other in both ruby1.8 and ruby1.9.
> Also, they are different in the same way :-)
>
> * in ruby1.8, proc {} is a synonym for lambda {}
>
> * in ruby1.9, proc {} is a synonym for Proc.new {}
>
> So to play it safe, never use proc {} - always use lambda {} or Proc.new {}

The original plan, as of RubyConf 2004, was to deprecate proc
entirely. At least, I got Matz to say he would on that occasion :-) I
rather wish that had happened. In any case, there's also ->(){} in 1.9
of course....


David

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