From: repeatr <repeater@...>
Date: 2003-05-17T06:12:09+09:00
Subject: Re: procs and context



> -----Original Message-----
> From: Kent Dahl [mailto:kentda@stud.ntnu.no]
> Sent: 16 May 2003 08:21
> To: ruby-talk ML
> Subject: Re: procs and context
> 
> 
> repeatr wrote:
> >   def live(&block)
> >     instance_eval { Proc.new.call }
> 
> Why not just
>      instance_eval( &block ) 
> which appears to work fine for me. The variable block points to a Proc
> of the external block already due to the &-prefix.

Ah that's it! That one flew straight by underneath the radar.
Even for my supposedly accustomed ruby mind, things fudge up. :-)

> 
> Or are you getting at something more complex? 
> 
> As for why it your original code doesn't work:
>   instance_eval { Proc.new.call }
> instance_eval only changes the context of the given block (which
> contains Proc.new.call), but Proc.new.call fetches another block/Proc
> (&block) from the outside of the method, and _that_ Proc does NOT get
> its context changed by instance_eval. Why should it? It would make
> recursive use of Procs a nightmare.

Rightly so.
Thank you kindly for the explanation and fix.

with regards
Peter