Tyson Richard DOWD
trd at cs.mu.oz.au
Thu Jun 12 14:39:04 AEST 1997
> How about adding this predicate to the library?
> It is used 11 times in muz so it must be useful :-)
That's funny, I thought the same thing about cut in my LPT project ;-)
I've added list__map_foldl to the library.
Estimated hours taken: 0.2
Add list__map_foldl/5, an amalgam of list__map and list__foldl.
This predicate was provided by Philip Dart.
Mention this addition. Add arity to mentions of list__foldl2 and
RCS file: /home/staff/zs/imp/mercury/NEWS,v
retrieving revision 1.51
diff -u -r1.51 NEWS
--- NEWS 1997/06/12 04:19:35 1.51
+++ NEWS 1997/06/12 04:32:41
@@ -184,8 +184,10 @@
lists using a user-specified procedure to write the elements and separating
the elements with a user-specified separator string.
- - We've added a double accumulator version of list__foldl called
- list__foldl2, which is a convenient generalisation for accumulators
- that also do I/O.
+ - We've added a double accumulator version of list__foldl/4 called
+ list__foldl2/6, which is a convenient generalisation for accumulators
+ that also do I/O. Also, we've added have list__map_foldl/5, which is an
+ amalgam of list__map/3 and list__foldl/4.
RCS file: /home/staff/zs/imp/mercury/library/list.m,v
retrieving revision 1.71
diff -u -r1.71 list.m
--- list.m 1997/06/12 04:19:41 1.71
+++ list.m 1997/06/12 04:29:53
@@ -402,6 +402,17 @@
:- mode list__foldl2(pred(in, di, uo, di, uo) is det,
in, di, uo, di, uo) is det.
+ % list__map_foldl(Pred, InList, OutList, Start, End) calls Pred
+ % with an accumulator (with the initial value of Start) on
+ % each element of InList (working left-to-right) to transform
+ % InList into OutList. The final value of the acumulator is
+ % returned in End.
+:- pred list__map_foldl(pred(X, Y, Z, Z), list(X), list(Y), Z, Z).
+:- mode list__map_foldl(pred(in, out, di, uo) is det, in, out, di, uo) is det.
+:- mode list__map_foldl(pred(in, out, in, out) is det, in, out, in, out) is det.
+:- mode list__map_foldl(pred(in, out, in, out) is semidet, in, out, in, out)
+ is semidet.
% list__sort_and_remove_dups(Compare, Unsorted, Sorted) is true iff
@@ -892,6 +903,12 @@
list__foldl2(P, [H|T], FirstAcc0, FirstAcc, SecAcc0, SecAcc) :-
call(P, H, FirstAcc0, FirstAcc1, SecAcc0, SecAcc1),
list__foldl2(P, T, FirstAcc1, FirstAcc, SecAcc1, SecAcc).
+list__map_foldl(_, , ) -->
+list__map_foldl(P, [H0|T0], [H|T]) -->
+ P(H0, H),
+ list__map_foldl(P, T0, T).
list__foldr(_, , Acc, Acc).
list__foldr(P, [H|T], Acc0, Acc) :-
Tyson Dowd #
# Surreal humour isn't eveyone's cup of
trd at cs.mu.oz.au # fur.
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