Menu
Search

Forums

Forum Index

February 28
Gravatar of Liam McGillivrayPosted by Liam McGillivrayReply
Liam McGillivray
Gravatar of Liam McGillivray


Reply

In D, it appears that dynamic arrays (at least by default) use a ulong as their key type. They are declared like this:

string[] dynamicArray;

I imagine that using a 64-bit value as the key would be slower than using 32 bits or 16 bits, and 64 bits is way overkill for nearly everything. However, if I declare the array as string[uint] myArray; or string[ushort] myArray, it's treated as an associative array. This means that I don't get to do the things I want to do with a dynamic array, such as appending.

So I have some questions:

Is there a way to declare a dynamic array with a uint, ushort, or ubyte key?

If there was, would it really be faster?

Is an associative array with a ushort key faster than a dynamic array with a ulong key?

February 27
Gravatar of H. S. TeohPosted by H. S. Teoh
in reply to Liam McGillivray		Reply
H. S. Teoh
Gravatar of H. S. Teoh
Posted in reply to Liam McGillivray


Reply
On Wed, Feb 28, 2024 at 03:00:55AM +0000, Liam McGillivray via Digitalmars-d-learn wrote:
> In D, it appears that dynamic arrays (at least by default) use a ulong
> as their key type. They are declared like this:
> ```
> string[] dynamicArray;
> ```
> 
> I imagine that using a 64-bit value as the key would be slower than using 32 bits or 16 bits,

Wrong. The machine uses 64 bits internally anyway.  Well, 48 on i386. But the point is that there is no speed difference.

Also, on 32-bit architectures size_t is aliased to uint, which is 32 bits.


[...]
> So I have some questions:
> 
> Is there a way to declare a dynamic array with a uint, ushort, or ubyte key?

No.


> If there was, would it really be faster?

No.


> Is an associative array with a ushort key faster than a dynamic array with a ulong key?

No.


T

-- 
Error: Keyboard not attached. Press F1 to continue. -- Yoon Ha Lee, CONLANG