I'm trying to write a routine to parse a string containing a series of
parameters of the form
KEYWORD = VALUE
or just
KEYWORD (where the value defaults to 1)
I was able to write it using a WHILE loop, but then thought I'd try using the
'g' option of s/// to do the iteration.
It seems to parse correctly-formed strings fine, but it is not *failing* to
match an incorrectly-formed string.
The following is what I've got so far. $line is set to a valid string, while
$badline is set to an invalid one - which, nevertheless, is parsed (partially)
as valid.
(Incidentally, as I post this I don't know whether my lines will be
hard-wrapped at some ridiculous length like 60, thus screwing up the code by
wrapping my regex comments. What causes that to happen? and, more to the
point, is that something I can override in my POP client?)
Also - if there's a module I should be using instead of re-inventing the wheel,
I'd appreciate knowing about it. But in any event, I'd like to understand why
my approach isn't working.
Here's the code. Thanks for any help.
Chap
- - - - -
#!/usr/bin/perl
use warnings;
use strict;
use feature ":5.10";
#
# $line, unless empty, should contain one or more white-space-separated
# expressions of the form
# FOO
# or BAZ = BAR
#
# We need to parse them and set
# $param{FOO} = 1 # default if value is omitted
# $param{BAZ} = 'BAR'
#
# Valid input example:
# MIN=2 MAX = 12 WEIGHTED TOTAL= 20
# Yields:
# $param{MIN} = '2'
# $param{MAX} = '12'
# $param{WEIGHTED} = 1
# $param{TOTAL} = '20'
#
my $line = 'min=2 max = 12 weighted total= 20';
my $badline = 'min=2 max, = 12 weighted total= 20';
my %param;
if ( $line and
($line !~
s/
\G # Begin where prev. left off
(?: # Either a parameter...
(?: # Keyword clause:
(\w+) # KEYWORD (captured $1)
(?: # Value clause:
\s* #
= # equal sign
\s* #
(\w+) # VALUE (captured $2)
)? # Value clause is optional
)
\s* # eat up any trailing ws
| # ... or ...
$ # End of line.
)
/ # use captured to set %param
$param{uc $1} = ( $2 ? $2 : 1 ) if defined $1;
/xeg
) ) {
say "Syntax error: '$line'";
while (my ($x, $y) = each %param) {say "$x='$y'";}
exit;
}
while (my ($x, $y) = each %param) {say "$x='$y'";}
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