Perl Weekly Challenge 201: not satisfied!

This post presents my solutions to the Perl Weekly Challenge 201.
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:
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 201 - Task 1 - Raku Implementation

The first task was about searching for missing numbers in a given list of scattered (i.e., unordered) numbers. This is a matter of grepping every number in a range: 

sub MAIN( *@n where { @n.grep( * ~~ Int ) == @n.elems } ) {
    my @missing-numbers;
    for 0 ^.. @n.elems {
    	@missing-numbers.push: $_ if ( ! @n.grep( $_ ) );
    }

    @missing-numbers.join( ', ' ).say;

}


PWC 201 - Task 2 - Raku Implementation

The second task is much more complex than the first one, and it involves computing the integer partitions for a given input number. It turned out that this task is too much difficult for me to solve, and that’s why I’m not satisfied in using an external library to achieve the result. However, thanks to Math::Combinatorics, I can use the partitions method that gives me the result: 

use Math::Combinatorics <partitions>;

sub MAIN( Int $n where { $n > 0 } ) {
    say partitions( $n ).elems;
}


PL/Perl Implementations

A very similar implementation to the Raku one, so I do grep for a given number in the input list:

PWC 201 - Task 1 - PL/Perl Implementation



CREATE OR REPLACE FUNCTION
pwc201.task1_plperl( int[] )
RETURNS SETOF int
AS $CODE$
   my ( $n ) = @_;

   for my $needle ( 1 .. $n->@* ) {
       return_next( $needle ) if ( ! grep( { $_ == $needle } $n->@* ) );
   }

return;
$CODE$
LANGUAGE plperl;


PWC 201 - Task 2 - PL/Perl Implementation

Again, I had to involve an external library, this time Integher::Partitions. 

CREATE OR REPLACE FUNCTION
pwc201.task2_plperl( int)
RETURNS int
AS $CODE$

  use Integer::Partition;
  my $partitions = Integer::Partition->new( $_[0] );
  my $count = 0;
  $count++  while( $partitions->next );
  return $count;
$CODE$
LANGUAGE plperlu;


This means that the code has to be written as plperlu, i.e., it is untrusted. Moreover, the Integer::Partiton library does provide only an iterative interface, so I need to manually count all the partitions before returning the result.

PostgreSQL Implementations

PWC 201 - Task 1 - PL/PgSQL Implementation

The first task can be solved with a simple SQL query: 

CREATE OR REPLACE FUNCTION
pwc201.task1_plpgsql( n int[] )
RETURNS SETOF int
AS $CODE$
   SELECT v
   FROM generate_series( 1, array_length( n, 1 ) ) v
   WHERE v NOT IN
   ( SELECT unnest( n ) );
$CODE$
LANGUAGE sql;


The function accepts an array and transforms it into a table by means of the unnest function. The result is then joined with the result of generate_series, a function that produces a sequences of integers. I keep only the tuples that do not match, meaning I’m keeping all the numbers that are not in the original array.

PWC 201 - Task 2 - PL/PgSQL Implementation

Again, I’m not satisfied of this solution! Since it is not simple to achieve this in SQL, I decided to simply call the PL/Perl implementation, that in turns calls an external module function, and this means there is nothing out of my bag here! 

CREATE OR REPLACE FUNCTION
pwc201.task2_plpgsql( n int )
RETURNS int
AS $CODE$
   SELECT pwc201.task2_plperl( n );
$CODE$
LANGUAGE sql;


The article Perl Weekly Challenge 201: not satisfied! has been posted by Luca Ferrari on January 23, 2023

Tags: raku , perlweeklychallenge , perl