:- module range_extraction.
:- interface.

:- import_module io.

:- pred main(io::di, io::uo) is det.

:- implementation.

:- import_module int, list, ranges, string.

main(!IO) :-
    print_ranges(numbers, !IO).

:- pred print_ranges(list(int)::in, io::di, io::uo) is det.

print_ranges(Nums, !IO) :-
    Ranges = ranges.from_list(Nums),
    ranges.range_foldr(add_range_string, Ranges, [], RangeStrs),
    io.write_list(RangeStrs, ",", io.write_string, !IO).

:- pred add_range_string(int::in, int::in,
     list(string)::in, list(string)::out) is det.

add_range_string(L, H, !Strs) :-
   ( if L = H then
      !:Strs = [int_to_string(L) | !.Strs]
   else if L + 1 = H then
      !:Strs = [int_to_string(L), int_to_string(H) | !.Strs]
   else
      !:Strs = [string.format("%d-%d", [i(L), i(H)]) | !.Strs]
   ).

:- func numbers = list(int).

numbers = [
   0,  1,  2,  4,  6,  7,  8, 11, 12, 14,
   15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
   25, 27, 28, 29, 30, 31, 32, 33, 35, 36,
   37, 38, 39].