day13

Makefile

@@ -1,7 +1,5 @@
-MMCFLAGS := \
-  --infer-all --warn-unused-imports
-  # this seems to break day7 for some absolutely bizarre reason
-  # -s asm_fast.par.gc.stseg
+MMCFLAGS := --infer-all --no-inform-inferred --warn-unused-imports \
+  -s asm_fast.par.gc.stseg
 
 all: aoc
 

aoc.m

@@ -47,6 +47,8 @@ run_day(Day, Part, Lines, Out) :-
 :- import_module day9.
 :- import_module day10.
 :- import_module day11.
+% :- import_module day12.
+:- import_module day13.
 
 :- pred solution(int::in, sol::out(sol)) is semidet.
 solution(1, day1.run).
@@ -60,3 +62,5 @@ solution(8, day8.run).
 solution(9, day9.run).
 solution(10, day10.run).
 solution(11, day11.run).
+% solution(12, day12.run).
+solution(13, day13.run).

day13.m

@@ -0,0 +1,86 @@
+:- module day13.
+:- interface.
+:- import_module basics.
+
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
+
+:- implementation.
+:- import_module int.
+:- import_module string.
+:- import_module list.
+
+:- type packet ---> i(int); l(list(packet)).
+:- type packets == {packet, packet}.
+
+
+:- pred packets(list(packets)::out, lines::in) is nondet.
+packets(Ps, Lines) :- packets(Ps, to_char_list(join_list("", Lines)), []).
+
+:- pred packets(list(packets)::out, chars::in, chars::out) is multi.
+packets([{P, Q} | Rest]) --> packet(P), packet(Q), packets(Rest).
+packets([])              --> [].
+
+:- pred packet(packet::out, chars::in, chars::out) is nondet.
+:- import_module day4.
+packet(i(I))  --> day4.number(I).
+packet(l(Ps)) --> ['['], inner(Ps), [']'].
+
+:- pred inner(list(packet)::out, chars::in, chars::out) is multi.
+inner(Ps) --> inner1(Ps).
+inner([]) --> [].
+
+:- pred inner1(list(packet)::out, chars::in, chars::out) is nondet.
+inner1([P | Ps]) --> packet(P), (if [','] then inner1(Ps) else {Ps = []}).
+
+
+:- pred cmps(list(packet)::in, list(packet)::in, comparison_result::out) is det.
+cmps([],     [],     =).
+cmps([],     [_|_],  <).
+cmps([_|_],  [],     >).
+cmps([P|Ps], [Q|Qs], C) :-
+  cmp(P, Q, C1), (if C1 = (=) then cmps(Ps, Qs, C) else C = C1).
+
+:- pred cmp(packet::in, packet::in, comparison_result::out) is det.
+cmp(i(I),  i(J),  C) :- compare(C, I, J).
+cmp(l(Ps), l(Qs), C) :- cmps(Ps,     Qs,     C).
+cmp(i(I),  l(Qs), C) :- cmps([i(I)], Qs,     C).
+cmp(l(Ps), i(J),  C) :- cmps(Ps,     [i(J)], C).
+
+:- func cmp(packet, packet) = comparison_result.
+cmp(P, Q) = C :- cmp(P, Q, C).
+
+:- pred ok(packets::in) is semidet.
+ok({P, Q}) :- not cmp(P, Q, >).
+
+div1 = l([l([i(2)])]).
+div2 = l([l([i(6)])]).
+
+:- pred divider(packet::in) is semidet.
+divider(div1). divider(div2).
+
+:- mode unary == (pred(in) is semidet).
+
+:- pred indices(pred(T)::unary, int::in, list(T)::in, list(int)::out) is det.
+indices(_, _, [],     []).
+indices(P, I, [X|Xs], Is) :-
+  indices(P, I + 1, Xs, Is0),
+  (if P(X) then Is = [I|Is0] else Is = Is0).
+
+:- pred indices(pred(T)::unary, list(T)::in, list(int)::out) is det.
+indices(P, Xs, Is) :- indices(P, 1, Xs, Is).
+
+
+:- func merge(list(packets)) = list(packet).
+merge(Ps) = foldl(func({X, Y}, Zs) = [X,Y|Zs], Ps, []).
+
+:- pragma no_determinism_warning(run/3).
+run(one, Lines, int(sum(Is))) :-
+  if packets(Ps, Lines) then
+    indices(ok, Ps, Is)
+  else
+    die("bad input").
+run(two, Lines, int(prod(Is))) :-
+  if packets(Pairs, Lines) then
+    indices(divider, sort(cmp, [div1, div2 | merge(Pairs)]), Is)
+  else
+    die("bad input").