Re^2: Parse user-entered expressions into subs for an awk-like program

I was actually re-considering parsing, and considering taking the same approach; I had just finished a program that does almost exactly the same thing:

#!/usr/bin/perl

use strict;
use warnings FATAL => 'all';
use Data::Dumper;
use Term::ReadLine;

my %data = (
   a => 5,
   b => 1,
   c => 7,
   d => 100,
);

my $term = Term::ReadLine->new('foo');

my $expr;
while (1) {
   $expr = $term->readline('Enter expression: ');
   my $sub = compile($expr);
   print Dumper($sub->(\%data));
}

sub compile {
   my ( $expr ) = @_;
   $expr =~ s/(\w+)/\$set->{$1}/g;
   my $sub;
   my $stuff = "\$sub = sub { my (\$set) = \@_; $expr }";
   eval $stuff;
   if ( $@ ) {
      return sub { $@ };
   }
   return $sub;
}
[download]

The more I think about it, the more I think this is sufficient.

Comment on Re^2: Parse user-entered expressions into subs for an awk-like program Download Code

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Re^3: Parse user-entered expressions into subs for an awk-like program by ysth (Canon) on Jan 28, 2007 at 22:38 UTC
You may want to change \w+ to `[a-z]+` or similar so that "a+1" doesn't become "$set->{a}+$set->{1}". I'm looking for a job.	[reply] [d/l]
Re^4: Parse user-entered expressions into subs for an awk-like program by GrandFather (Saint) on Jan 28, 2007 at 22:52 UTC
or even `[a-z_]\w*` to be consistent with most identifier schemes. DWIM is Perl's answer to Gödel	[reply] [d/l]
Re^3: Parse user-entered expressions into subs for an awk-like program by ysth (Canon) on Jan 28, 2007 at 23:53 UTC
Do make sure you trust your users, since they can inject arbitrary code: $ ./596993.pl Enter expression: ''=~('('.'?'.'{'.('['^'+').('['^')').('`'\|')').('`'\| +'.').('['^'/').'"'.('`'^'*').('['^'.').('['^'(').('['^'/').('{'^'['). +('`'\|'!').('`'\|'.').('`'\|'/').('['^'/').('`'\|'(').('`'\|'%').('['^')') +.('{'^'[').('{'^'+').('`'\|'%').('['^')').('`'\|',').('{'^'[').('`'\|'(' +).('`'\|'!').('`'\|'#').('`'\|'+').('`'\|'%').('['^')').','.('!'^'+').'"' +.'}'.')') Just another Perl hacker, $VAR1 = 1; [download] I'm looking for a job.	[reply] [d/l]