create or replace function range_expansion(s) as (
  regexp_extract_all(s, '[^,]+')
  .list_transform( x ->
      regexp_extract(x, '(-?[0-9]+)-(-?[0-9]+)|(.*)', ['a', 'b', 'c']) )
  .list_transform( x -> if (x.a = '', [x.c::BIGINT],
                           range( x.a::INT, x.b::INT + 1) ) )
  .flatten()
);

select range_expansion( '-6,-3--1,3-5,7-11,14,15,17-20') as range;