10.09.2012 18:37, monarch_dodra пишет:
There is a know bug: foreach with ref does not currently work these
containers. The reason is that the container's front does not actually
expose a reference, but a value, and that is what is being changed (the
returned value).
There is no hope in sight to really *ever* make it work, because
"container.front += 5" can't be made to work if the returned value is
not a reference: Unlike indexes that define opIndexOpAssign, there is no
opFrontOpAssign.
What bothers *me* though is that the code compiles fine, biting more
than 1 user in the process.
Anyways... the workaround is* making an explicit loop, with temporary
object that is fed back into front, like this:
import std.container;
--------
void main()
{
// double-linked list;
DList!int dlist;
dlist.insertFront(0);
auto slice = dlist[]; //Extract a range manually
for( ; !slice.empty ; slice.popFront() )
{
auto value = slice.front; //Extract the value
value += 50; //Increment the value
slice.front() = value; //Feed back into the range*
}
foreach(value; dlist) {
assert(value == 50); //Now this works fine
}
}
--------
Well... this *would* work, but apparently, the implementation of
DList.Range doesn't define front(T value). This makes the Range pretty
much read-only. My guess is that this was an omission on the part of the
implementer. I will fix it so that it works.
Good to know, but bad to do...
If in std.container:
1553: @property T front() { return _first._payload; }
change to:
1553: @property *ref* T front() { return _first._payload; }
doesn't it solve the problem or I don't know/understand something else?
