Yes, the line count_characters([H|T], #{ H := N }=X) -> … is not yet fully understood by the VM. More details on this here [1]. Every other line works fin

Yes, the line count_characters([H|T], #{ H := N }=X) -> … is not yet fully understood by the VM. More details on this here [1]. Every other line works fine though. Oh and instead of using maps one can use records, dicts, sets, gb_trees, proplists, … [1] http://stackoverflow.com/questions/23106543/illegal-pattern-in-map-of-erlang http://stackoverflow.com/questions/23106543/illegal-pattern-...