CREATE OR REPLACE FUNCTION int2range_diff(IN int2, IN int2) RETURNS float8 AS $$
    SELECT int2mi($1, $2)::float8;
$$ LANGUAGE SQL IMMUTABLE PARALLEL SAFE STRICT;

CREATE TYPE public.int2range AS RANGE (
    SUBTYPE         = int2,
    SUBTYPE_OPCLASS = int2_ops,
    CANONICAL       = int2range_canonical,
    SUBTYPE_DIFF    = int2range_diff
);