From bug-octave-request at bevo dot che dot wisc dot edu Tue Dec  3 11:37:05 2002
Subject: return, continue, break -> ans = 1
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Miroslaw Kwasniak <mirek at infrared dot zind dot ikem dot pwr dot wroc dot pl>
Cc: bug-octave at bevo dot che dot wisc dot edu,    Etienne Grossmann <etienne@isr.isr.ist.utl.pt>,    Pascal.Dupuis@esat.kuleuven.ac.be,    octave-maintainers mailing list <octave-maintainers@bevo.che.wisc.edu>
Date: Tue, 3 Dec 2002 11:36:52 -0600

On 29-Nov-2002, Miroslaw Kwasniak <mirek at infrared dot zind dot ikem dot pwr dot wroc dot pl> wrote:

| To: bug-octave at bevo dot che dot wisc dot edu
| Cc: mirek
| Subject: return, continue, break -> ans = 1
| 
| Bug report for Octave 2.1.40 configured for i386-pc-linux-gnu
| 
| Description:
| -----------
| 
| Hi,
| 
|   Control statements: return, continue, break 
| 
|   If they are last statements in a line (not followed by semicolon)
|   octave displays: ans = 1

This is happening because of some changes I made in response to 
http://www.octave.org/mailing-lists/bug-octave/2002/154.  The idea was
to make Octave's break, continue, and return statements behave more
like they do in Perl.  For example, make

  some_expression || break;

work as it would in Perl.  To implement this within the current
parser/interpreter, break must be an expression that returns a value.
But as people have pointed out, that causes a few other surprises for
existing Octave code.

My changes were simple.  They just made break, continue, and return do
what did before, but also behave as functions that returned 1 so they
would be valid in logical contexts.  But a simple change is not good
enough, and I don't see a way to allow the Perl-like behavior and also
be backward compatible without making some major changes to the way
Octave's parser and interpreter work.  I don't think it is worth the
effort and I've undone the changes I made earlier.  The CVS archive
should be updated within a few minutes.

jwe



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