From 6eb6f4bd15ee85683a4e7057cbe0c8e3b0c49cbe Mon Sep 17 00:00:00 2001
From: rhiannon morris <rhi@rhiannon.website>
Date: Sat, 3 Dec 2022 11:24:35 +0100
Subject: [PATCH] no more char lists in day3

---
 day3.m | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/day3.m b/day3.m
index afaf431..c8eea59 100644
--- a/day3.m
+++ b/day3.m
@@ -11,12 +11,17 @@
 :- import_module char.
 :- import_module string.
 
-:- pred split(chars::in, chars::out, chars::out) is semidet.
+:- pred split(string::in, string::out, string::out) is semidet.
 split(X, L, H) :-
   Len = length(X), even(Len),
-  split_list(Len / 2, X, L, H).
+  split(X, Len / 2, L, H).
 
-:- pred common(list(chars)::in, char::out) is nondet.
+:- pred member(char::out, string::in) is nondet.
+member(C, S) :-
+  nondet_int_in_range(0, length(S) - 1, I),
+  index(S, I, C).
+
+:- pred common(list(string)::in, char::out) is nondet.
 common([S | Ss], C) :- member(C, S), (Ss = [] ; common(Ss, C)).
 
 :- func prio(char) = int.
@@ -36,7 +41,7 @@ threes([X, Y, Z | Rest], [t(X, Y, Z) | Groups]) :- threes(Rest, Groups).
 
 :- pred go1(string::in, int::out) is cc_multi.
 go1(Line, Out) :-
-  if split(to_char_list(Line), Fst, Snd),
+  if split(Line, Fst, Snd),
      common([Fst, Snd], C)
   then
     Out = prio(C)
@@ -46,11 +51,10 @@ go1(Line, Out) :-
 
 :- pred go2(triple(string)::in, int::out) is cc_multi.
 go2(t(X, Y, Z), Prio) :-
-  if common(map(to_char_list, [X, Y, Z]), C) then
+  if common([X, Y, Z], C) then
     Prio = prio(C)
   else
-    die("no item in common in:\n - %s\n - %s\n - %s",
-        [s(X), s(Y), s(Z)]).
+    die("no item in common in:\n - %s\n - %s\n - %s", [s(X), s(Y), s(Z)]).
 
 
 run(one, Lines, univ(sum(Prios))) :-