From: "Hal E. Fulton" <hal9000@...>
Date: 2003-03-31T07:57:35+09:00
Subject: Re: how to catch any exception "eval" throws

----- Original Message ----- 
From: "Meinrad Recheis" <meinrad.recheis@aon.at>
Newsgroups: comp.lang.ruby
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Sunday, March 30, 2003 4:31 PM
Subject: how to catch any exception "eval" throws


> i tried
> 
> begin
> eval( str )
> rescue
> puts $!
> end
> 
> but my program terminates if str contains erraneous expressions
> why doesn t rescue catch say "parser errors"?

I can never remember exactly how this works, 
but the default is to catch a certain family
of errors (perhaps StandardError? I'm probably
misleading you).

Putting a very general class there would help,
perhaps 'rescue Exception' -- but I'm not sure
that is correct.
 
> this is from the book:
> 
> eval( aString [, aBinding [ file [ line ] ] ]) -> anObject
> 
> i have no guess how to use this. what do the nested [] mean?

That simply means that the parameters are 
independently optional. These are all 
valid:

  eval(a,b,f,l)
  eval(a,b,f)
  eval(a,b
  eval(a)

HTH,
Hal