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;
You are printing the contents of $_ but you don't have anything in $_
until the next line.
> $_ = <>;
> } while (/^\s*$/ 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?
> }
Perhaps this is what you want:
sub print_lines_ideal {
my ( $output, $blank_lines ) = @_;
my $expr = $blank_lines ? qr/^\s*$/ : qr/\S/;
while ( <> ) {
print if $output and /$expr/;
}
}
John
--
use Perl;
program
fulfillment
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