On Wed, 26 Jun 2013 11:57:55 +0100 Rob Dixon <rob.di...@gmx.com> wrote:
> On 26/06/2013 10:32, Shlomi Fish wrote: > >> > >> Hi, > >> > >> Could you please let me know how to reverse a string without using built > >> in function. > > > > Do you want to avoid using the > > http://perldoc.perl.org/functions/reverse.html built-in function or any > > built-in function whatsoever? Assuming the latter you can do this: > > Sorry, I meant that he wished to avoid using reverse() only - not any built-in function whatsoever. > > [CODE] > > #!/usr/bin/perl > > > > use strict; > > use warnings; > > > > sub my_reverse > > { > > my ($s) = @_; > > > > my $ret = ""; > > > > for my $idx (0 .. length($s) - 1) > > { > > $ret = substr($s, $idx, 1) . $ret; > > } > > > > return $ret; > > } > > > > my $string = shift(@ARGV); > > > > print "Reversed is:\n", my_reverse($string), "\n"; > > [/CODE] > > > > Running it gives you: > > > > [SHELL] > > > > shlomif@telaviv1:~$ perl my-reverse.pl Hello > > Reversed is: > > olleH > > shlomif@telaviv1:~$ perl my-reverse.pl Franklin > > Reversed is: > > nilknarF > > shlomif@telaviv1:~$ > > > > [/SHELL] > > I don't understand. You say you are providing a solution that avoids > "any built-in function whatsoever", and then use `length` and `substr`. Yes, see above. Here is a solution without any built-in functions, but with some built-in operators: <CODE> #!/usr/bin/perl use strict; use warnings; sub my_reverse { my ($s) = @_; my $ret = ""; my @chars = ($s =~ /(.)/gms); foreach my $c (@chars) { $ret = $c . $ret; } return $ret; } my ($string) = @ARGV; print "Reversed is:\n", my_reverse($string), "\n"; </CODE> You can also do something similar without keeping an array of characters using something like /\G(.)/gms . Regards, Shlomi Fish -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ Optimising Code for Speed - http://shlom.in/optimise Judaism: God knows you will do shit, does nothing to prevent it, but makes you take the blame for it anyways. Please reply to list if it's a mailing list post - http://shlom.in/reply . -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
