Brian H. Oak <> wrote:
> Mathieu,
>
> Thank you, you gave me just the clue I needed! BTW, the parameter
> thing is required or else it returns a blank string. Here's what
> works:
>
> ############################################################
> # Position and character would normally be determined # by user
> input, but are hard-coded here for brevity
> my $position = 2; # Is always a number, 1-4
> my $character = "~"; # Can be any "special" char
>
> # Build substitution for later use
> my $substitute;
> if ( $position == 1 ) { # s/^(.*)$/~$1/
> $substitute = sub { $_[0] =~ s/^(.*)$/$character$1/; return $_[0] }; }
> elsif ( $position == 2 ) { # s/^(.*)(\.[^.]+)$/$1~$2/
> $substitute = sub { $_[0] =~ s/^(.*)(\.[^.]+)$/$1$character$2/;
> return $_[0] }; }
> elsif ( $position == 3 ) { # s/^(.*\.)([^.]+)$/$1~$2/
> $substitute = sub { $_[0] =~ s/^(.*\.)([^.]+)$/$1$character$2/;
> return $_[0] }; }
> elsif ( $position == 4 ) { # s/^(.*)$/$1~/
> $substitute = sub { $_[0] =~ s/^(.*)$/$1$character/; return $_[0] };
> } else { die "Invalid position: $position\n"; }
>
> # Loop thousands of times
> for ( 0..99_000 ) {
> # Filename would be different every time
> my $filename = "filename.plus.ext";
> #$filename = $substitute->( $filename );
> $substitute->( $filename );
> print "$filename\n";
> }
> ############################################################
Actually you don't need the return. In a subroutine the elements of @_
are aliases to the original parameters, so modifying $_[0] modifies (or
tries to) the original parameter. See 'perldoc perlsub'. If you want to
use a return value (which would be my personal preference for this sort
of thing), you should localise the parameter before changing it in the
sub (i.e. "my"), and assign the return value where you call the sub.
Also, that "if" statement screams "array" to me. Plus, you don't need a
regexp matching operation to simply add a single character to the start
or end of a string. So, I think your code could be a bit simpler...
use strict;
use warnings;
my $character = '~';
my $position = 4;
my @transforms
= (sub { $_[0] = "${character}$_[0]" },
sub { $_[0] =~ s/(\.[^.]+)$/${character}$1/; },
sub { $_[0] =~ s/([^.]+)$/${character}$1/; },
sub { $_[0] = "$_[0]${character}" }
);
my $sub = $transforms[$position - 1];
defined $sub or die "Invalid position: $position\n";
for (0..10) {
my $filename = "filename.plus.ext";
$sub->($filename);
print "$filename\n";
}
(Note the use of "use strict; use warnings;". I strongly recommend them
both.)
HTH
--
Brian Raven
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