Second class pointers

[ZombineDev via Digitalmars-d-learn]

On Friday, 8 July 2016 at 06:17:43 UTC, Nicholas Wilson wrote:
> On Friday, 8 July 2016 at 05:53:21 UTC, Nicholas Wilson wrote:
>> So as part of my effort to get D running on GPUs I need to 
>> make a "second class" pointer type that I can alter in the 
>> backend of LDC to the correct address space. to that end I 
>> have made the following
>>
>> module dcompute.types.pointer;
>>
>> enum Private = 0;
>> enum Global = 1;
>> enum Shared = 2;
>> enum Constant = 3;
>> enum Generic = 4;
>>
>> pure @trusted nothrow @nogc
>> struct Pointer(uint p, T) if(p <= Generic)
>> {
>>     T* ptr;
>>     ref T opUnary(string op)() if(op=="*")
>>     {
>>         return *ptr;
>>     }
>>     ref T opIndex(size_t i)
>>     {
>>         return *(ptr+i);
>>     }
>>     auto opBinary(string op)(ptrdiff_t i) if(op=="+" || op == 
>> "-")
>>     {
>>          return Pointer!(p, T) (ptr + i);
>>     }
>> }
>>
>> ...
>
> That should be mixin("ptr"~op~"i")
> I need compound add and compound subtract as well.

Why not make the address (memory) space a strongly-typed enum, 
e.g.:

enum AddressSpace
{
     threadLocal = 0,
     groupLocal = 1,
     global = 2,
     constant = 3,
     texture = 4
     generic = 5
}

struct Pointer(T, AddressSpace type = AddressSpace.Generic)
// ...

?

>> is there anything else that I'm missing that you can do with a 
>> raw pointer?

Slicing:

// Pseudo OpenCL-D

groupLocal T* ptr1;
groupLocal T[] slice1 = ptr1[2 .. 10];

global T* ptr2;
groupLocal T[] slice2 = ptr2[0 .. 2]; // Error