proposal: searching in array function - array_position

Implementation is simple (plpgsql code)

CREATE OR REPLACE FUNCTION array_position(anyarray, anyelement)
RETURNS int AS $$
DECLARE i int := 0;
BEGIN
  FOREACH a IN ARRAY $1
  LOOP
    IF a = $1 THEN
      RETURN i;
    END IF;
    i := i + 1;
  END LOOP;
  RETURN NULL;
END;
$$ LANGUAGE plpgsql IMMUTABLE STRICT;