Finding the context of a call: numerical or string

casiano has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

Is there any way to know if my sub was called in a "numerical" context or a "string" context?

use strict;

sub sensible {
  return "one" if stringcontext();
  return 1 if numericalcontext();
  return;
}

print "Result = ".sensible()."\n";   # Result = one
print "Result = ".0+sensible()."\n"; # Result = 1
[download]

A partial solution is to use dualvar from Scalar::Util but then I have to compute both the string and the number on each call.

Many thanks

Casiano

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Re: Finding the context of a call: numerical or string by kyle (Abbot) on Feb 29, 2008 at 16:35 UTC
See Contextual::Return. Update: According to the synopsis, this should work for you: `sub sensible { return STR { "one" } NUM { 1 } }` [download]	[reply] [d/l]
Re^2: Finding the context of a call: numerical or string by casiano (Pilgrim) on Feb 29, 2008 at 16:58 UTC
Many thanks! It works! Casiano	[reply]
Re^3: Finding the context of a call: numerical or string by sgt (Deacon) on Mar 02, 2008 at 12:52 UTC
Hi Casiano, Take into account that Contextual::Return uses Want. Maybe you can manage to do what you need with Want alone. Is caching + dualvar an option? cheers --stephan p.d maybe you could visit madrid.pm one of these days? ;)	[reply]
Re: Finding the context of a call: numerical or string by ikegami (Patriarch) on Feb 29, 2008 at 17:19 UTC
Or you can create a dualvar using `dualvar` in core module Scalar::Util. Then, the returned value with be both a string and a number. `use Scalar::Util qw( dualvar ); sub sensible { return dualvar(1, "one"); } my $foo = sensible(); print "Result = ", ''.$foo, "\n"; # Result = one print "Result = ", 0+$foo, "\n"; # Result = 1` [download] Very fast too. Nothing special as far as Perl is concerned.	[reply] [d/l] [select]
Re: Finding the context of a call: numerical or string by leocharre (Priest) on Feb 29, 2008 at 16:56 UTC
There's something called contextual return which sounds sexy, but... I understand this may be a performance hit. I would't use this kind of thing in anything that's supposed to go fast or do something crazy without user interaction. deserves looking into. (wow, Damian Conway sure does make a lot of juicy stuff..)	[reply]
Re^2: Finding the context of a call: numerical or string by TGI (Parson) on Feb 29, 2008 at 20:03 UTC
Apparently, it's even one of his "safe" modules. TGI says moo	[reply]