Perl Weekly Challenge 185: string substitutions
It is sad that, after more than three years of me doing Raku, I still don’t have any production code project to work on. Therefore, in order to keep my coding and Raku-ing (is that a term?) knowdledge, I try to solve every Perl Weekly Challenge tasks.In the following, the assigned tasks for Challenge 185.
and for the sake of some Perl 5, let’s do some stuff also in PostgreSQL Pl/Perl:
Last, the solutions in PostgreSQL PL/PgSQL:
PWC 185 - Task 1
Given a mac address in the formaaaa.aaaa.aaaa provide the well know form aa:aa:aa:aa:aa:.
It is quite simple to do this:
sub MAIN( Str $input-mac-address
where { $input-mac-address ~~ / ^ ( <[0..9a..f]> ** 4 <[.]> ) ** 2 <[0..9a..f]> ** 4 $ / } ) {
my $output-mac-address = $input-mac-address.subst( /<[.]>/, '', :g );
$output-mac-address.comb( :spit-empty ).rotor( 2 ).join( ':' ).subst( /\s+/, '', :g ).say;
}
The regular expression in the parameter list ensures that the input is what I expect to be. Then I remove the dots within the mac address, obtaining a string-only representation, that then I split and recombine in groups of
2 letters via rotor, append a : at the array join operation and remove all the spaces.
PWC 185 - Task 2
Substitute the first four digits or letters found in a set of random strings.sub MAIN( *@codes ) {
my @output-codes;
for @codes -> $current-code {
my @current-output;
my $counter = 4;
for $current-code.comb -> $current-char is copy {
$current-char = 'x'
and $counter--
if $current-char ~~ / <[0..9a..z]> / && $counter > 0;
@current-output.push: $current-char;
}
@output-codes.push: @current-output.join;
}
@output-codes.join( "\n" ).say;
}
The idea is to to split every string into its array of chars, and then keep track with a
$counter of how many I need to substitute. I recombine the chars into the @current-output array that is then printed as a string.
PWC 185 - Task 1 in PostgreSQL PL/Perl
A very similar implementation to the Raku one.CREATE OR REPLACE FUNCTION
pwc185.task1_plperl( text )
RETURNS text
AS $CODE$
my ( $input ) = @_;
$input =~ s/\./g/;
my ( $counter, $output ) = ( 1, '' );
for ( split( //, $input ) ) {
$output .= $_;
$output .= ':' if $counter % 2 == 0;
$counter++;
}
return $output;
$CODE$
LANGUAGE plperl;
This time I keep a
$counter that holds how many chars I’ve already placed in the final mac address string, and each time I get a multiple of 2 I place also a :.
PWC 185 - Task 2 in PostgreSQL PL/Perl
Similar to the Raku implementation, but accepts a single string as input.CREATE OR REPLACE FUNCTION
pwc185.task2_plperl( text )
RETURNS text
AS $CODE$
my ( $input ) = @_;
my @output;
my $counter = 4;
for ( split( //, $input ) ) {
push @output, 'x'
and $counter--
and next if ( /[a-z0-9]/i ) and $counter > 0;
push @output, $_;
}
return join( '', @output );
$CODE$
LANGUAGE plperl;
PWC 185 - Task 1 in PostgreSQL PL/PgSQL
A reimplementation of the PL/Perl approach.CREATE OR REPLACE FUNCTION
pwc185.task1_plpgsql( mac_input text )
RETURNS text
AS $CODE$
DECLARE
c int := 1;
d char;
mac_output text := '';
BEGIN
mac_input := replace( mac_input, '.', '' );
FOREACH d IN ARRAY regexp_split_to_array( mac_input, '' ) LOOP
mac_output := mac_output || d;
IF c % 2 = 0 THEN
mac_output := mac_output || ':';
END IF;
c := c + 1;
END LOOP;
RETURN mac_output;
END
$CODE$
LANGUAGE plpgsql;
PWC 185 - Task 2 in PostgreSQL PL/PgSQL
Similar approach than the PL/Perl one. I use the~ regular expression match operator to quickly understand if the character I’m analysing is a digit, a letter or none of the above.
CREATE OR REPLACE FUNCTION
pwc185.task2_plpgsql( code text )
RETURNS text
AS $CODE$
DECLARE
how_many int := 4;
d char;
code_out text := '';
BEGIN
FOREACH d IN ARRAY regexp_split_to_array( code, '' ) LOOP
IF how_many = 0 OR d !~ '\w' THEN
code_out := code_out || d;
CONTINUE;
ELSEIF how_many > 0 AND d ~ '\w' THEN
code_out := code_out || 'x';
how_many := how_many - 1;
ELSE
code_out := code_out || d;
END IF;
END LOOP;
RETURN code_out;
END
$CODE$
LANGUAGE plpgsql;