postgresql: pivot table according to row_names, categories and values

crosstab.sql

select * from crosstab($$
  select row_name, some_category, some_value --only 3 columns!
  from some_table
$$, $$values(category1), (category2), ..., (categoryn)$$ -- same can be achieved by selecting distinct values
) as g(RowName type, Category1 type, Category2 type, ..., CategoryN type);
-- type of CategoryN should be the same as type of value