Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!jpl-devvax!lwall
From: lwall@jpl-devvax.jpl.nasa.gov (Larry Wall)
Newsgroups: comp.lang.perl
Subject: Re: alpha numbers
Message-ID: <1991Jun24.231628.14446@jpl-devvax.jpl.nasa.gov>
Date: 24 Jun 91 23:16:28 GMT
References: <1991Jun23.200134.18835@pronto.mh.nl>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 41

In article <1991Jun23.200134.18835@pronto.mh.nl> Johan Vromans <jv@mh.nl> writes:
: Perl 4.010, System Ultrix/RISC, GCC compiled.
: 
: Exhibit 1:
: 
: 	$a = "1a";
: 	$b = $a + 1;
: 
: I would have expected an error (or at least a warning).

Would you have expected an error for this?

	$a = "1\n";
	$b = $a + 1;

There are many times when you want it to ignore the rest of the string just
like atof() does.  Oddly enough, Perl calls atof().  How convenient.  :-)

If you want to make sure your number is a number all the way to the end,
/^\d+$/ works just fine.  I'm reticent to force that overhead on everyone,
however.

: Exhibit 2:
: 
: 	$a = "1a";
: 	$a++;
: 
: IMHO, the correct value for $a should now be "1b", not 2.

Okay, tell me the correct value for this:

	$a = "1e0";
	$a++;

Hint: it ain't "1e1".  It may be that limiting magical increment to
values matching /^[A-za-z]*[0-9]*$/ is overkill, but you can usually
get what you want by concatenation.  I suppose I could relax it to
allow /^[A-Za-z]\w*/ as well.  I doubt I'll ever allow magical increment
on anything starting with digits unless it's all digits.

Larry