Thanks for the tips! More comments below.
On Tue, Nov 3, 2009 at 4:10 AM, John W. Krahn <jwkr...@shaw.ca> wrote:
> tom smith wrote:
>
>> On Mon, Nov 2, 2009 at 7:41 PM, Remy Guo <rollingst...@gmail.com> wrote:
>>
>> i've got problem when trying to perform a substitution.
>>>
>>> the text file i want to process is like this:
>>> ...
>>> XXXXXX {
>>> ABDADADGA
>>> afj*DHFHH
>>> } (a123)
>>> XXDFAAF {
>>> af2hwefh
>>> fauufui
>>> } (b332)
>>> ...
>>>
>>> i want to match the content in the parenthesis (a123 and b332, here) and
>>> replace them with a sorted number (0;0, 0;1, 0;2, .... 0; 255, 1;0,
>>> 1;1, ...1; 255, for example), so i wrote the script like this:
>>> if (m/\}.*\(.*\)/)
>>> {
>>> $j++;
>>> if ($j >= 255)
>>> {
>>> $i++;
>>> $j = 0;
>>> }
>>>
>>> $_ =~ s/\(.*\)/$i;$j/
>>> }
>>>
>>> now the problem is that, i'm sure the matching
>>> regex successfully matches the line that i want, but the subsitution just
>>> don't happen. why?...
>>>
>>
>> First, the s/// operator applies to $_ by default.
>>
>> Second, as far as I can tell there's no indication anywhere in your script
>> as to what the value of $_ might be.
>>
>> This works for me:
>>
>> use strict;
>> use warnings;
>>
>> open(my $INFILE, "<", "in.txt");
>> open(my $OUTFILE, ">", "out.txt");
>>
>
> You should *always* verify that the files have been opened correctly before
> trying to use a possibly invalid filehandle.
>
> open my $INFILE, '<', 'in.txt' or die "Cannot open 'in.txt' $!";
> open my $OUTFILE, '>', 'out.txt' or die "Cannot open 'out.txt' $!";
Whoops!
>
>
>
> my $line;
>> my $i = 0;
>> my $j = 0;
>>
>> while ($line = <$INFILE>) {
>>
>
> There is no need for $line to be in file scope:
>
> while ( my $line = <$INFILE> ) {
>
>
Shoot. Normally, I write it like you did, but I saw it written the other
way somewhere, and I thought it looked cleaner. I'll do it your way from
now on.
>
> if ($line =~ /\((.*?)\)/) {
>>
>> $line =~ s/$1/$i;$j/;
>>
>
> If you have two regular expressions that are doing the same thing then you
> are probably doing it incorrectly:
>
> if ( $line =~ s/\((.*?)\)/($i;$j)/ ) {
>
Ah. Nice.
>
> $j++;
>> if ($j > 255) {
>>
>
> The OP wanted to go from 0 to 255 but this goes from 0 to 254.
>
>
>>
Yes. You're wrong, though about what my code does. The if statement
doesn't evaluate to true unless $j == 256.
Thanks for the suggestions. I appreciate it.
