Re^5: regular expression

Tou forgot to unset your flag

#!/usr/bin/perl

use strict;
use warnings;
my $flag=0;
while(<DATA>){
        if (/\{AUTHOR\}/){
                $flag=1;
                next;
        }
        if (/^\{/){
                $flag=0;
                next;
        }
        print $_ if $flag;
}


__DATA__
{TAG}
tag1
{AUTHOR}
By June Fletcher
JOURNAL
{TAG}
tag2
TOM MacCUBBIN
{DATA}
data1
{AUTHOR}
Richard White
{AUTHOR}
MacCUBBIN
{SOUR}
[download]

Comment on Re^5: regular expression Download Code

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Re^6: regular expression by vitoco (Hermit) on Aug 16, 2009 at 20:37 UTC
Tou forgot to unset your flag No, the flag is being set with the result of the expression: `$1 eq "AUTHOR"` Moving the condition to the second line (bad idea, because the expression will be evaluated many times even if $tag does not change for some rows): `my $tag = ""; while (<DATA>) { ($tag = $1, next) if /\{(\w+)\}/; print $_ if $tag eq "AUTHOR"; }` [download] Removing the `next` from the tricky array used to have 2 sentences being affected by the `if` condition to test for a line with braces: `my $tag = ""; while (<DATA>) { $tag = $1 if /\{(\w+)\}/; next if /\{/; print $_ if $tag eq "AUTHOR"; }` [download] Too many evaluations of conditional expressions. Inefficient, but I guess you got the idea. BTW, I was assuming that braces won't appear on text lines... `my $flag = 0; while (<DATA>) { $flag = ($1 eq "AUTHOR") if /^\{(\w+)\}$/; print $_ if $flag and not /^\{/; }` [download]	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^6: regular expression
by vitoco (Hermit) on Aug 16, 2009 at 20:37 UTC

Tou forgot to unset your flag

No, the flag is being set with the result of the expression: $1 eq "AUTHOR"

Moving the condition to the second line (bad idea, because the expression will be evaluated many times even if $tag does not change for some rows):

my $tag = "";
while (<DATA>) {
    ($tag = $1, next) if /\{(\w+)\}/;
    print $_ if $tag eq "AUTHOR";
}
[download]

Removing the next from the tricky array used to have 2 sentences being affected by the if condition to test for a line with braces:

my $tag = "";
while (<DATA>) {
  $tag = $1 if /\{(\w+)\}/;
  next if /\{/;
  print $_ if $tag eq "AUTHOR";
}
[download]

Too many evaluations of conditional expressions. Inefficient, but I guess you got the idea.

BTW, I was assuming that braces won't appear on text lines...

my $flag = 0;
while (<DATA>) {
  $flag = ($1 eq "AUTHOR") if /^\{(\w+)\}$/;
  print $_ if $flag and not /^\{/;
}
[download]

[reply]
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