first

.gitignore

@@ -0,0 +1,4 @@
+Mercury/
+*.mh
+*.err
+aoc

aoc.m

@@ -0,0 +1,42 @@
+:- module aoc.
+:- interface.
+:- import_module io.
+
+:- pred main(io::di, io::uo) is cc_multi.
+
+:- implementation.
+:- import_module basics.
+:- import_module die.
+:- import_module string.
+:- import_module list.
+:- import_module exception.
+
+main(!IO) :- wrap_main(main2, !IO).
+
+:- pred main2(io::di, io::uo) is cc_multi.
+:- pragma no_determinism_warning(main2/2).
+main2(!IO) :-
+  command_line_arguments(Args, !IO),
+  (if (Args = [DayS, PartS | Rest],
+       to_int(DayS, Day),
+       part(PartS, Part))
+   then
+    run(Day, Part, Rest, !IO)
+   else if Args = [D, P | _] then
+    die("expected a day and a part, got ""%s"" ""%s""", [s(D), s(P)])
+   else
+    die("expected at least two args")).
+
+:- type solution == (pred(part, list(string), io, io)).
+:- inst solution == (pred(in, in, di, uo) is det).
+
+:- pred solution(int::in, solution::out(solution)) is semidet.
+solution(_, _) :- fail.
+
+:- pred run(int::in, part::in, list(string)::in, io::di, io::uo) is det.
+
+run(Day, Part, Args, !IO) :-
+  if solution(Day, P) then
+    P(Part, Args, !IO)
+  else
+    die("no solution for day %d", [i(Day)]).

basics.m

@@ -0,0 +1,13 @@
+:- module basics.
+:- interface.
+
+:- type part ---> one; two.
+
+:- pred part(string, part).
+:- mode part(in,  out) is semidet.
+:- mode part(out, in)  is semidet.
+
+:- implementation.
+
+part("1", one).
+part("2", two).

die.m

@@ -0,0 +1,29 @@
+:- module die.
+:- interface.
+:- import_module io.
+:- import_module list.
+:- import_module string.
+
+:- pred die(string::in) is erroneous.
+:- pred die(string::in, list(poly_type)::in) is erroneous.
+
+:- type main == (pred(io, io)).
+:- inst main == (pred(di, uo) is cc_multi).
+
+:- pred wrap_main(main::in(main), io::di, io::uo) is cc_multi.
+
+:- implementation.
+:- import_module exception.
+
+:- type die ---> death(string).
+
+die(Str) :- throw(death(Str)).
+die(Fmt, Args) :- die(format(Fmt, Args)).
+
+wrap_main(Main, !IO) :-
+  try [io(!IO)] Main(!IO)
+  then true
+  catch death(Err) -> (
+    format("%s\n", [s(Err)], !IO),
+    set_exit_status(1, !IO)
+  ).