in reply to RE: keeping $$this defined locally
in thread keeping $$this defined locally

A program reads in a template (not mine) which has fields defined 

first=one
second=two

then it reads in another file with stuff like

"adding $first and $second we get third"

i loop through the variables from the template, and pretty
much do this for each one (assume $newstring points at the
string above):

{
($variable, $value) = split("=", $linefromtemplate);
$$variable = $value;
$newstring = eval("return \"$newstring\");
}

Not beautiful I agree...but seemed a quick way of doing what
I want - only I dont want the newly associated variables
to be applicable outside of the scope of the block they 
are declared in.

(And strict complains about it too)

Thanks

Specimen

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RE (tilly) 3: keeping $$this defined locally
by tilly (Archbishop) on Oct 04, 2000 at 19:32 UTC
    That template looks like it was written for a shell.

    Anyways I would use a hash for the keys and regular expression substitution. So the first file would be read like: 

    my @entry = split(/=/, $line, 2);
$val{$entry[0]} = $entry[1];

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    and then substitute them in with: 
    s/\$(\w+)/exists($val{$1})?$val{$1}:die "Undefined '$1' in entry '$new
+string' (line $.)"/eg;

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    Now strict should be happy, and things are easy to scope. Plus I stuck a minimal error check in.

    Oh, and strangle the person who wrote the stupid template willya?

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      Yup - combining a few messy sh scripts into a perl one.

      Thanks. I'll try doing that - i was actually going to do that initially - thought i'd take the easy route out and let eval do all my work for me though.

      Specimen
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RE: RE: RE: keeping $$this defined locally
by princepawn (Parson) on Oct 04, 2000 at 19:38 UTC
  • You probably should use a high-quality templating CPAN module, such as Template or Text::Template
  • If you insist on homegrowing your tmeplate module, the chief means of isolating variables within Perl are packages or hashes.
    1. For hashes, here's a snippet: 
      {
   my %template_var;

   my ($key,$val) = split '=', $linefromtemplate;
   $template_var{$key} = $val;
}

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    2. And for packages, here's another: 
      {
   package template_var;

   my ($key,$val) = split '=', $linefromtemplate;
no strict 'refs';
  $$key = $val;# left out symbolic dereference
use strict 'refs';
}

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      I woulda caught my error if we could preview replies to other posts...Why dont we enable that?

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