On 10/30/2011 6:45 PM, Jonathan M Davis wrote:
On Sunday, October 30, 2011 11:38:30 Max Wolter wrote:
Hello there.
I seem to be having problems wrapping my head around how to use the
ranges in the context of containers in phobos. Specifically, I can't
seem to figure out how to remove an element from a linked list.
foreach(cell; organism)
{
if(cell.x == x&& cell.y == y)
{
organism.stableLinearRemove(cell);
break;
}
}
mind.d(123): Error: function
std.container.SList!(Cell).SList.linearRemove (Range r) is not callable
using argument types (Cell)
mind.d(123): Error: cannot implicitly convert expression (cell) of type
cell.Cell to Take!(Range)
I somehow get the feeling such a basic operation should just...work?
linearRemove (and stableLinearRemove) takes a _range_ not a value. cell is an
element in the list, not a range over the list. The range that it takes must
be either of type SList.Range or Take!(SList.Range). You get that range by
slicing an SList. Take!(SList.Range) is for the case where you want only a
portion of the beginning of a range rather than the whole range. Your example
actually has a really simple solution:
auto found = find!((a){return a.x == x&& a.y == y;})(organism[]);
organism.stableLinearRemove(take(found, 1));
It finds the element in the list that you're looking for, and then it passes a
range with that one element to stableLinearRemove so that it'll remove it.
- Jonathan M Davis
Hello there.
Thank you very much for the explanation.
However, while I really liked the concept of ranges in Andrei's book and
a lot of it seems intuitive and faster than using iterators, I can't
shake the feeling that in this case, it's just unnecessarily convoluted.
Maybe it's just the fact that the container library is still very basic,
but I don't think I should go through such a complicated procedure to
remove an known element from a list. It's just not a "very simple" or
intuitive solution, which is something I came to love D for thus far.
/Max
