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Re: Re: regex issue

by CountZero (Bishop)
on Mar 24, 2004 at 20:12 UTC ( #339536=note: print w/replies, xml ) Need Help??


in reply to Re: regex issue
in thread regex issue

<nitpicking mode="on">

++ for the code with the symbolic references, but the OP specifically wanted to have lexical variables ("my"). Is it at all possible to have symbolic references to lexical variables?

<nitpicking mode="off">

CountZero

"If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

Replies are listed 'Best First'.
Re: Re: Re: regex issue
by tilly (Archbishop) on Mar 24, 2004 at 21:11 UTC
    No. As perlref says, Only package variables (globals, even if localized) are visible to symbolic references. Lexical variables (declared with my()) aren't in a symbol table, and thus are invisible to this mechanism.

    If you want to access lexical variables, you have to do a lot of mucking around with internals. Modules (like PadWalker) can get rid of most of that for you. But I don't think that this module will actually create new lexical variables in the previous scope. Perhaps some module will do it. If not, then I'd bet that it is possible for someone knowledgable to write such a beast.

    However actually using it would not be recommended...

Re^3: regex issue
by Roy Johnson (Monsignor) on Mar 24, 2004 at 21:42 UTC
    You would have to do it with eval:
    use strict; use warnings; my $ref; my ($A,$B); while (<DATA>) { chomp; if (s/^\s+//) { eval "\$$ref = $_" } else {$ref = $_} } print "A=$A and B=$B\n"; __DATA__ A 33 B 22

    The PerlMonk tr/// Advocate
      No, no, that's cheating.

      You cannot predeclare my ($A,$B) as you are not supposed to know what's in the data-file. It could be any variable name and any value.

      However, the eval suggestion is a good one. How about:

      $name ='A'; $value =10; $string = 'my $' . $name . '=' . $value . '; print "result inside eval +: $A\n";'; eval ($string) or die "ERROR: $@"; print "result outside eval: $A\n";

      As can be expected the lexical declaration does not survive outside of the eval though :-(

      CountZero

      "If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law

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