From: "David A. Black" <dblack@...>
Date: 2004-10-05T03:31:14+09:00
Subject: Re: Kernel#eval taking a block

Hi --

On Tue, 5 Oct 2004, trans.  (T. Onoma) wrote:

> On Monday 04 October 2004 11:11 am, Yukihiro Matsumoto wrote:
> > Hi,
> >
> > In message "Re: Kernel#eval taking a block"
> >
> >     on Mon, 4 Oct 2004 23:23:22 +0900, "trans.  (T. Onoma)" 
> <transami@runbox.com> writes:
> > |Back to the original question: why Kernel#eval can't take a block?
> >
> > Because it's useless, for my eyes at least.  What do you want to
> > accomplish by eval with a block?
> 
> How to get locals into evaluation?
> 
>  class T
>     def initialize
>      @x = 1
>    end
>    attr_reader :x
>    def get_binding
>      cool = "matz"
>      return binding()
>    end
>  end
>  t = T.new
>  tb = t.get_binding
>  eval "cool", tb  #=> "matz"
>  a = proc {|c| c.upcase}
>  eval "cool = a.call(cool)", tb
> 
> NameError: undefined local variable or method `a' for #<T:0x4032f038 @x=1>
>         from (irb):15:in `get_binding'
>         from (irb):15:in `get_binding'
>         from (irb):19

But if you're eval'ing in another binding, 'a' won't mean anything in
a string or a block, will it?  In other words: you're trying to mix
locals from two bindings in one expression, which somewhat defeats the
purpose of having "locals" :-)


David

-- 
David A. Black
dblack@wobblini.net