Perl Weekly Challenge 231: min, max and regexp!

This post presents my solutions to the Perl Weekly Challenge 231.
I keep doing the Perl Weekly Challenge in order to mantain my coding skills in good shape, as well as in order to learn new things, with particular regard to Raku, a language that I love.
This week, I solved the following tasks:

PWC 231 - Task 1 - Raku
PWC 231 - Task 2 - Raku
PWC 231 - Task 1 in PostgreSQL PL/Perl
PWC 231 - Task 2 in PostgreSQL PL/Perl
PWC 231 - Task 1 in PostgreSQL PL/PgSQL
PWC 231 - Task 2 in PostgreSQL PL/PgSQL

The PL/Perl implementations are very similar to a pure Perl implementation, even if the PostgreSQL environment could involve some more constraints. Similarly, the PL/PgSQL implementations help me keeping my PostgreSQL programming skills in good shape.

Raku Implementations

PWC 231 - Task 1 - Raku Implementation

The first task was about extracting all the numbers on a given array of integers excluding the min and max values.

sub MAIN( *@nums where { @nums.elems == @nums.grep( * ~~ Int ).elems } ) {
    my @wanted;
    @wanted.push: $_ if ( @nums.min < $_ < @nums.max ) for @nums;
    @wanted.join( ',' ).say;
}

PWC 231 - Task 2 - Raku Implementation

The second task was about counting passengers with an age greater than sixty years, given that each passenger data is coded in way that can be easily handled with a regular expression.

sub MAIN( *@passengers ) {
    my $count = 0;
    for @passengers {
	next if $_ !~~ / ^ (\d ** 10 ) (<[MF]>) (\d ** 2 ) (\d ** 2) $ /;
	my ( $phone, $gender, $age, $seat ) = $/.Array;
	$count++ if ( $age >= 60 );
    }

    $count.say;
}

PL/Perl Implementations

PWC 231 - Task 1 - PL/Perl Implementation

This time I decided to implement a min and max functions by myself, so that I can cache the results and loop over the given array to compare every value with the above two.

CREATE OR REPLACE FUNCTION
pwc231.task1_plperl( int[] )
RETURNS SETOF int
AS $CODE$
   my ( $nums ) = @_;

   my $min = sub {
      my ( $array ) = @_;
      my $min = undef;

      for ( $array->@* ) {
      	  $min = $_ if ( not defined( $min ) || $_ < $min );
      }

      return $min;
   };


   my $max = sub {
      my ( $array ) = @_;
      my $max = $array->[ 0 ];
      for ( $array->@* ) {
      	  $max = $_ if ( $_ > $max );
      }

      return $max;
   };


   my ( $min_value, $max_value ) = ( $min->( $nums ), $max->( $nums ) );
   for ( $nums->@* ) {
       return_next( $_ ) if ( $_ > $min_value && $_ < $max_value );
   }

   return undef;


$CODE$
LANGUAGE plperl;

PWC 231 - Task 2 - PL/Perl Implementation

Here, it is probably even simpler than the Raku implementation, thanks to capturing of regular expressions.

CREATE OR REPLACE FUNCTION
pwc231.task2_plperl( text[] )
RETURNS int
AS $CODE$
   my ( $passengers ) = @_;
   my $count = 0;

   for ( $passengers->@* ) {
       if ( / ^ \d{10} [MF] (\d{2}) \d{2} $ /x ) {
          $count++ if ( $1 >= 60 );
       }
   }

   return $count;
$CODE$
LANGUAGE plperl;

PostgreSQL Implementations

PWC 231 - Task 1 - PL/PgSQL Implementation

A single query to extract all the values, skipping the min and max coming out of a inner query each.

CREATE OR REPLACE FUNCTION
pwc231.task1_plpgsql( nums int[] )
RETURNS SETOF int
AS $CODE$
	SELECT
	v
	FROM unnest( nums ) v
	WHERE v <> ( SELECT max( vv ) FROM unnest( nums ) vv )
	AND   v <> ( SELECT min( vv ) FROM unnest( nums ) vv )
	;
$CODE$
LANGUAGE sql;

PWC 231 - Task 2 - PL/PgSQL Implementation

Here I took a slightly different approach to solve it within a single query. The age view materializes a set of record, each one made by an array of text[] because that’s the result of regexp_matches. I know every record will be made by a single cell array, so in the end, it just suffice to count the number of records.

CREATE OR REPLACE FUNCTION
pwc231.task2_plpgsql( passengers text[] )
RETURNS int
AS $CODE$

   WITH ages( a ) as (
     SELECT regexp_matches( v::text, '^\d{10}[MF]([6-9]\d)\d{2}$')::text
     FROM unnest( passengers ) v
   )
   SELECT count(*)
   FROM ages



$CODE$
LANGUAGE sql;

In order to avoid the mess of converting a text[] to an int and compare the value, I included in the regexp the selector to skip every age that is lower than sixty.

The article Perl Weekly Challenge 231: min, max and regexp! has been posted by Luca Ferrari on August 21, 2023

Tags: raku , perlweeklychallenge , perl