From: daz <dooby@...10.karoo.co.uk>
Date: 2003-06-25T15:55:23+09:00
Subject: Re: Another Run Time Evaluation Q:


"Shashank Date" <sdate@everestkc.net> wrote:
>
> "Orion Hunter" <orion2480@hotmail.com> wrote in message
> > However, why does this not work?
>
> I can answer this part. Please see "ri eval" output for more details:
>
>      As of Ruby 1.8, local variables assigned within an eval are
>      only available after the eval if they were defined at the outter
>      scope before the eval executed. In this way eval has the same
>      scoping rules as blocks.
>
> > $>ruby -e 'str = "a = 2"; eval(str); puts a'
> > -e:1: undefined local variable or method `a' for #<Object:0x124b00>
> > (NameError)
> >
> > p.s.  If I do the equivalent in IRB, it remembers the variable name.
>
> I don't know how irb manages to do it : some "binding" magic I guess.
> Can experts shed some light please?
>
> -- shanko
>

Invoking "Hunt & Thomas" Programming Ruby - (Addison Wesley Longman) ...

Chapter:  Interactive Ruby Shell
Section:  Restrictions

[... Excellent description ...]

IMO, Ruby's behaviour conforms to PoMS in this area.
                          (L=Least, M=Most or Maximum).
- I would call it 'bonkers' :@


printf("ruby %s (%s) [%s]\n", RUBY_VERSION, RUBY_RELEASE_DATE, RUBY_PLATFORM)
#d='I refuse to uncomment this'
eval('d=10')
p d rescue eval('d+1')

eval('d=12')
p d rescue eval('d+1', TOPLEVEL_BINDING)
p d

#-> ruby 1.7.3 (2002-11-17) [i386-mswin32]
#-> 11
#-> 13
#-> rb31D4.TMP:8: undefined local variable or method `d'
# for #<Object:0x258d4c8> (NameError)


daz