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+--
+-- Perl Weekly Challenge 242
+-- Task 2
+--
+-- See <https://perlweeklychallenge.org/blog/perl-weekly-challenge-242/>
+--
+
+CREATE SCHEMA IF NOT EXISTS pwc242;
+
+/*
+estdb=> select pwc242.task2_plpgsql( array[1,0,0,0,0,0,0,1,1]::int[], 3 );
+ task2_plpgsql
+---------------
+ {1,1,0}
+ {1,1,1}
+ {0,0,1}
+(3 rows)
+*/
+CREATE OR REPLACE FUNCTION
+pwc242.task2_plpgsql( matrix int[], l int )
+RETURNS SETOF int[]
+AS $CODE$
+DECLARE
+ current_row text;
+ current int;
+ index int;
+ to_return int;
+ result int[];
+BEGIN
+ index := 1;
+ current_row := '';
+
+ FOREACH current IN ARRAY matrix LOOP
+ current_row := current_row || current::text;
+ IF index = l THEN
+ -- the row is now complete, flip and split
+ result := array[]::int[];
+ FOREACH to_return IN ARRAY regexp_split_to_array( reverse( current_row ), '' ) LOOP
+ IF to_return = 1 THEN
+ result := array_append( result, 0 );
+ ELSE
+ result := array_append( result, 1 );
+ END IF;
+ END LOOP;
+
+ RETURN NEXT result;
+
+ -- start over
+ current_row := '';
+ index := 1;
+ ELSE
+ index := index + 1;
+ END IF;
+ END LOOP;
+
+ RETURN;
+END
+$CODE$
+LANGUAGE plpgsql;