Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer

get name of lexical variable

by khwilliamson (Initiate)
on Jul 12, 2009 at 17:14 UTC ( #779385=perlquestion: print w/replies, xml ) Need Help??
khwilliamson has asked for the wisdom of the Perl Monks concerning the following question:

I have a subroutine which is passed a reference to a lexical variable like foo(\$lex). Is there a way to find the string 'lex' in that subroutine? Thanks in advance

Replies are listed 'Best First'.
Re: get name of lexical variable
by moritz (Cardinal) on Jul 12, 2009 at 17:46 UTC

    Just an idea, don't know if it might work:

    You could use PadWalker to sniff your caller's lexicals and see if the reference address of any of them is equal to the reference you've got.

      PadWalker provides a var_name function that takes the reference and does that for you. It's even more reliable than looping over the lexicals, when the lexical you want is hidden:
      #!/usr/bin/perl -l use strict; use warnings; use PadWalker ":all"; sub foo { my $x; for ($x) { my $x; bar(\$_); } } sub bar { print var_name(1, $_[0]); # works my $vars = peek_my(1); print grep $vars->{$_} == $_[0], keys %$vars; # doesn't work unle +ss 2nd my $x is commented out } foo();
Re: get name of lexical variable
by psini (Deacon) on Jul 12, 2009 at 17:41 UTC

    Dunno, but it makes little sense to me. For you can have an anonymous reference. (no name) or you can have a reference to a scalar that has more than one name (using Scalar::Alias or similar)

    So the question "which is the name of the var referenced by $x" may have zero, one or more than one answer.

    Is yours an academic question or have you a specific need in mind? Maybe it is an XY Problem.

    Rule One: "Do not act incautiously when confronting a little bald wrinkly smiling man."

Re: get name of lexical variable
by mzedeler (Pilgrim) on Jul 12, 2009 at 20:30 UTC

    If you need that information, you are breaking a number of encapsulation rules that are really bad to break.

    Could you explain why you want to do this in the first place?

      One could write a nice subroutine useful in debugging, whic when called in the following way:

      my $aLex=25; print(display($aLex),"\n");
      would print
      $aLex == 25

      Ronald Fischer <>

        I agree that there are uses for a subroutine that can return such names as requested, but usually when people ask for something like this, its a sign of a more mundane problem solved in the wrong way.

Log In?

What's my password?
Create A New User
Node Status?
node history
Node Type: perlquestion [id://779385]
Front-paged by Arunbear
and !@monks...

How do I use this? | Other CB clients
Other Users?
Others meditating upon the Monastery: (4)
As of 2017-10-17 02:31 GMT
Find Nodes?
    Voting Booth?
    My fridge is mostly full of:

    Results (218 votes). Check out past polls.