From 2af4043f6a09ec65d09a171acbd52b302db78c14 Mon Sep 17 00:00:00 2001
From: rhiannon morris <rhi@rhiannon.website>
Date: Fri, 16 Dec 2022 16:29:37 +0100
Subject: [PATCH] foldl_index & map_index

---
 basics.m | 64 ++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 53 insertions(+), 11 deletions(-)

diff --git a/basics.m b/basics.m
index bf2444a..452571e 100644
--- a/basics.m
+++ b/basics.m
@@ -15,8 +15,7 @@
 :- pred output(answer::in, io::di, io::uo) is det.
 
 
-:- func ite((pred), T, T) = T.
-:- mode ite((pred) is semidet, in, in) = out is det.
+:- func ite((pred)::((pred) is semidet), T::in, T::in) = (T::out) is det.
 
 
 :- import_module list.
@@ -46,8 +45,27 @@
 :- func replicate(int, T) = list(T).
 :- func rev_sort(list(T)) = list(T).
 
+
 :- func map_index(func(int, T) = U, list(T)) = list(U).
 
+:- pred map_index(pred(int, T, U), list(T), list(U)).
+:- mode map_index(pred(in, in, out) is det,      in, out) is det.
+:- mode map_index(pred(in, di, uo)  is det,      di, uo)  is det.
+:- mode map_index(pred(in, in, out) is semidet,  in, out) is semidet.
+:- mode map_index(pred(in, in, out) is multi,    in, out) is multi.
+:- mode map_index(pred(in, in, out) is cc_multi, in, out) is cc_multi.
+
+
+:- func foldl_index(func(int, T, U) = U, list(T), U) = U.
+
+:- pred foldl_index(pred(int, T, U, U), list(T), U, U).
+:- mode foldl_index(pred(in, in, in, out) is det,      in, in, out) is det.
+:- mode foldl_index(pred(in, in, di, uo)  is det,      in, di, uo)  is det.
+:- mode foldl_index(pred(in, di, di, uo)  is det,      di, di, uo)  is det.
+:- mode foldl_index(pred(in, in, in, out) is semidet,  in, in, out) is semidet.
+:- mode foldl_index(pred(in, in, in, out) is multi,    in, in, out) is multi.
+:- mode foldl_index(pred(in, in, in, out) is cc_multi, in, in, out) is cc_multi.
+
 
 :- import_module maybe.
 
@@ -59,8 +77,7 @@
 part("1", one).
 part("2", two).
 
-part(one, X, _) = X.
-part(two, _, Y) = Y.
+part(P, X, Y) = ite(unify(P, one), X, Y).
 
 
 output(int(I),    !IO) :- write_int(I, !IO), nl(!IO).
@@ -82,10 +99,9 @@ die(Fmt, Args) :- die(format(Fmt, Args)).
 wrap_main(Main, !IO) :-
   try [io(!IO)] Main(!IO)
   then true
-  catch death(Err) -> (
+  catch death(Err) ->
     format("%s\n", [s(Err)], !IO),
-    set_exit_status(1, !IO)
-  ).
+    set_exit_status(1, !IO).
 
 need(ok(X),    X).
 need(error(E), _) :- die(error_message(E)).
@@ -107,12 +123,38 @@ replicate(N, X) = Out :-
 
 rev_sort(Xs) = sort(converse(ordering), Xs).
 
-:- func map_index(int, func(int, T) = U, list(T)) = list(U).
-map_index(_, _, [])       = [].
-map_index(I, F, [X | Xs]) = [F(I, X) | map_index(I+1, F, Xs)].
 
-map_index(F, Xs) = map_index(0, F, Xs).
+:- pred map_index(int, pred(int, T, U), list(T), list(U)).
+:- mode map_index(in, pred(in, in, out) is det,      in, out) is det.
+:- mode map_index(in, pred(in, di, uo)  is det,      di, uo)  is det.
+:- mode map_index(in, pred(in, in, out) is semidet,  in, out) is semidet.
+:- mode map_index(in, pred(in, in, out) is cc_multi, in, out) is cc_multi.
+:- mode map_index(in, pred(in, in, out) is multi,    in, out) is multi.
+map_index(_, _, [], []).
+map_index(I, P, [X | Xs], [Y | Ys]) :- P(I, X, Y), map_index(I, P, Xs, Ys).
 
+map_index(P, Xs, Ys) :- map_index(0, P, Xs, Ys).
+map_index(F, Xs) = Ys :-
+  P = (pred(I::in, X::in, Y::out) is det :- Y = F(I, X)),
+  map_index(P, Xs, Ys).
+
+
+:- pred foldl_index(int, pred(int, T, U, U), list(T), U, U).
+:- mode foldl_index(in, pred(in, in, in, out) is det,      in, in, out) is det.
+:- mode foldl_index(in, pred(in, in, di, uo)  is det,      in, di, uo)  is det.
+:- mode foldl_index(in, pred(in, di, di, uo)  is det,      di, di, uo)  is det.
+:- mode foldl_index(in, pred(in, in, in, out) is semidet,  in, in, out) is semidet.
+:- mode foldl_index(in, pred(in, in, in, out) is multi,    in, in, out) is multi.
+:- mode foldl_index(in, pred(in, in, in, out) is cc_multi, in, in, out) is cc_multi.
+foldl_index(_, _, [],       !Acc).
+foldl_index(I, P, [X | Xs], !Acc) :-
+  P(I, X, !Acc),
+  foldl_index(I + 1, P, Xs, !Acc).
+
+foldl_index(P, Xs, !Acc) :- foldl_index(0, P, Xs, !Acc).
+foldl_index(F, Xs, Start) = End :-
+  P = (pred(I::in, X::in, A::in, B::out) is det :- B = F(I, X, A)),
+  foldl_index(P, Xs, Start, End).
 
 to_int_may(Str) = Out :-
   if to_int(Str, N) then Out = yes(N) else Out = no.