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.
You were very close to the answer:
auto makeMultidimensionalArray(int N, T, Allocator)(auto ref
Allocator alloc, size_t[N] lengths)
{
static if (lengths.length == 1)
{
return makeArray!T(alloc, lengths[0]);
}
else
{
alias E = typeof(makeMultidimensionalArray!(N-1,T)(alloc,
lengths[1..$]));
auto ret = makeArray!E(alloc, lengths[0]);
foreach (ref e; ret)
e = makeMultidimensionalArray!(N-1, T)(alloc,
lengths[1..$]);
return ret;
}
}
The key point is that return type depends on length of "lengths"
array (dimensionality), so if this length is only known at
runtime this is a dependent type, something D lacks (you'll need
Idris or Agda for those). In D return type must be known at
compile time and hence the length of "lengths" must be a compile
time argument. With such argument everything compiles smoothly.
