On Wednesday, 11 January 2017 at 19:23:10 UTC, Razvan Nitu wrote:
Hi,
I am currently trying to create a function
makeMultidimensionalArray which allocates memory for a
multidimensional array. It is very similar with [1],
the difference being that it is uninitialized. Here is the code:
auto makeMultidimensionalArray(T, Allocator)(auto ref Allocator
alloc, size_t[] lengths)
{
if (lengths.length == 1)
{
return makeArray!T(alloc, lengths[0]);
}
else
{
alias E = typeof(makeMultidimensionalArray!T(alloc,
lengths[1..$]));
auto ret = makeArray!E(alloc, lengths[0]);
foreach (ref e; ret)
e = makeMultidimensionalArray!T(alloc,
lengths[1..$]);
return ret;
}
}
The lengths[] specifies the lengths for each dimension. The
problem with this code is that auto is going to be evaluated to
T[] for the first time and when it
recurs, creating T[][] I get the error "mismatched function
return type inference of T[][] and T[]". Is there a way to
surpass that? I saw that in [1]
the recursive call is done by prefixing the function name with
a '.'; I tried that but it doesn't work. I must be missing
something, any ideas?
Thanks,
RazvanN
[1]
https://github.com/dlang/phobos/blob/master/std/experimental/ndslice/slice.d#L834
If you change the return type to a void* your code basically
works.
void* makeMultidimensionalArray(T, Allocator)(auto ref Allocator
alloc, size_t[] lengths)
{
if (lengths.length == 1)
{
int x = 0x01FEEF01;
return cast(void*)makeArray!T(alloc, lengths[0], x);
}
else
{
alias E = typeof(makeMultidimensionalArray!T(alloc,
lengths[1..$]));
auto ret = makeArray!E(alloc, lengths[0]);
foreach (ref e; ret)
e = makeMultidimensionalArray!T(alloc, lengths[1..$]);
return cast(void*)ret;
}
}
The problem is that then you need to cast back and that
essentially results in the original problem. Can be done but
probably gonna have to use string mixins.
