Path: utzoo!attcan!uunet!mcsun!sunic!uupsi!rpi!brutus.cs.uiuc.edu!zaphod.mps.ohio-state.edu!van-bc!ubc-cs!alberta!oha!tony
From: tony@oha.UUCP (Tony Olekshy)
Newsgroups: comp.lang.perl
Subject: Re: numeric from string
Summary: Use eval to force Perl's string base interpretation.
Message-ID: <407@oha.UUCP>
Date: 12 Mar 90 21:17:22 GMT
References: <13537@cbnewsd.ATT.COM> <7347@jpl-devvax.JPL.NASA.GOV>
Reply-To: tony@oha.UUCP
Organization: Olekshy Hoover & Associates Ltd., Edmonton, Alberta, Canada.
Lines: 38
In-Reply-To: Message <7347@jpl-devvax.JPL.NASA.GOV> dated 8 Mar 90 19:01:22 GMT
Return-Path: <alberta!oha!tony>

In message <7347@jpl-devvax.JPL.NASA.GOV>, lwall@jpl-devvax.JPL.NASA.GOV
(Larry Wall) writes:
|
| In article <13537@cbnewsd.ATT.COM> weiss@cbnewsd.ATT.COM (edward.j.weiss,ihp,)
| writes:
| : 
| : 	perl -e '$m="0777"; $n = $m + 1; print $n,"\n";'
| : 
| : What should the answer be? 
| : 
| : I would guess that 0777 would be converted to a number by
| : using 8 as a base, but it doesn't.  Base 10 is used.
| : MisFeature?
| 
| To stretch the example of oct() from the manual:
| 
| 	$mode = <>;
| 	$mode = oct($mode) if $mode =~ /^0/;
| 	chmod($mode, $file);
| 
| If you wanted to always interpret it as octal even if they didn't input
| the leading zero, you would just drop the if modifier.

If you have a numeric string $s and want to use Perl's leading 0 base
mechanism, use $n = eval("$s");  Note that you can force base conversion
to octal with $n = eval("0$s"); which is what I used in my chmod script.
Of course, I forgot about oct().

	perl -e '$s = "10"; print eval("$s"),"\n";'     --> 10
	perl -e '$s = "010"; print eval("$s"),"\n";'    --> 8
	perl -e '$s = "0x10"; print eval("$s"),"\n";'   --> 16

--
Yours, etc., Tony Olekshy (...!alberta!oha!tony or tony@oha.UUCP).

Just another perl.

[I'm sorry, I couldn't help it.  Now where's my velvet housecoat?]