Sam wrote:
>
> # Print lines (or not) until a blank line is found (or not)
>
> # This function works fine. But in the spirit of learning...read on.
>
> sub print_lines_ok {
>
> my ($output, $blank_lines) = @_;
>
> if ($blank_lines) {
> do {
> print if $output;
>
> $_ = <>;
>
> } while (/^\s*$/ and not eof);
> } else {
> do {
> print if $output;
>
> $_ = <>;
>
> } while (not /^\s*$/ and not eof);
> }
> }
>
>
> # This function is the same thing; just more 'elegant' IMHO. :-)
> # But it has its problems. I can eval it in the while loop and it
> # works as it is below, but it's painfully slow. I *know* there's no
> # need for the eval call every iteration but so far haven't figured
> # out how to use eval outside the while AND have it work. It
> # appears $expr is always true unless the eval is done in the while loop.
> # In summary, how can I build a dynamic regexp that I can eval once
> # and then use?
>
>
> sub print_lines_ideal {
>
> my ($output, $blank_lines) = @_;
> my $expr = $blank_lines ? '/^\s*$/' : 'not /^\s*$/';
>
> # eval $expr # I want to eval this ONCE and then use it. Help?
>
>
> do {
> print if $output;
>
> $_ = <>;
>
> } while (eval $expr and not eof); # works, but not fast.
> # Can I move eval out of loop?
> }
>
I don't think you want what you've written, as the first call to 'print'
is before anything has been read from the file. This should come close:
sub print_lines {
my ($output, $blank_lines) = @_;
while (<>) {
last if $blank_lines xor /\S/;
print if $output;
}
}
Rob
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
<http://learn.perl.org/> <http://learn.perl.org/first-response>
