On Friday, 19 June 2015 at 02:24:35 UTC, Andrei Alexandrescu
wrote:
On 6/18/15 6:26 PM, ZombineDev wrote:
On Friday, 19 June 2015 at 01:07:10 UTC, ZombineDev wrote:
On Thursday, 18 June 2015 at 23:32:03 UTC, Andrei
Alexandrescu wrote:
[..]
Yah, traditionally functional data structures don't allow their
clients to mutate the data AND the topology of the container.
So front() returns a non-mutable ref.
It might be interesting to explore containers that allow
mutation of data but not of topology. We may collectively think
of a few applications of that. For now I went the traditional
route.
Andrei
I just realized that my idea of something in between collections
and ranges obviously comes from D's own slices/dynamic arrays :D
(I really shouldn't be allowed to talk so late in the night :D)
So here's an idea - can we make the new functional SList (and
probably DList) the logic counter-part of slices?
const SList!int; // <- `const int[]` You can't mutate the
elements,
// nor the topology
SList!(const(int)); // <- `const(int)[]` You can mutate the
topology,
//but not the elements
ConstSList!(int); // <- `missing head const array` You can
mutate the elements,
// but not the topology
SList!(int); // <- `int[]` Unlimited power
SList!(int) mutable_list;
mutable_list ~= 3; //change the topology in-place
const SList!(int) const_list;
const_list ~= 42; //error - can't mutate const SList
const SList!(int) concat_result = const_list ~ 42;
//functional-style "modification"
foreach (elem; concat_result) {..} //error need mutable range,
because of popFront()
SList!(const(int)) range = concat_result; // implicitly
convertable
// like const(int)[] <-
const(int[])
foreach (elem; range) {..} // works
So instead of limiting the user by making `front` return const
refs, we allow him to choose.
