I was curious, is there any practical limit on the size of a set (32 bits and 256 values) and why they couldn’t be 64 bit or any other arbitrary size? The floor seems to be 4 bytes too but why not allow smaller sizes to save memory? Perhaps just a historical artifact but I was curious.

Regards,
Ryan Joseph

Sorry that was wrong, the biggest size is 32 bytes and the largest size of an enum is 256 elements. I was talking about sets of enums also if that wasn ’t clear.

I still don’t see it’s possible to make a set which is smaller than 4 bytes, even in the 0..7 range.

Regards,
Ryan Joseph

program Project1;
{$PackSet 1}
var
   a: set of byte;
   b: set of 0..7;
begin
   writeln(sizeof(a));
   writeln(sizeof(b));
   readln;
end.

Hairy Pixels via fpc-pascal schrieb am
Sa., 11. Jan. 2025, 14:17:

Set are a minimum of 4 Byte by default cause that's how Delphi does them. Ifets you want smaller sets then use the $PackSets directive as Martin had written.

The maximum is also based on what TP and Delphi allow. ISO Pascal for example suggests a maximum of 1024 elements instead, though they define this number to be implementation specific.
In the end it's a decision of where to do the cut as at some size the majority of the set will be sparsely populated so it makes more sense to use a dedicated type instead (e.g. a hash set or something like that) that wastes less memory.

Regards,
Sven

so it makes more sense to use a dedicated type instead (e.g. a hash set or something like that)

I found these implementations of hash set (origial is from Java, as search shows):

https://wiki.freepascal.org/LGenerics

- hashset (unit lgHashSet)
- fine-grained concurrent hashset (unit lgHashSet)
- disjoint set (unit lgHashSet)

Alex

I always use the one from generics.collections

On Jan 11, 2025 at 10:53:36 PM, Sven Barth via fpc-pascal <

I did not know this existed. I don’t see any reason they force the set to 4 bytes unless it was being used to pass to C libraries maybe?

Theoretically if you added one more element to 257 the size would double to 64 bytes right? That’s still only 50% of a short string both of which can be sparsely populate so how are they different?

Regards,
Ryan Joseph