[fpc-devel] Sets > 256

Jonas Maebe jonas.maebe at elis.ugent.be
Thu Oct 15 16:21:53 CEST 2015

DaWorm wrote on Thu, 15 Oct 2015:

> What if someone is storing a set in a file, or a stream?  Old version saves
> it, new version reads it, and all of the sudden the data isn't in the same
> format.

Support for larger sets would not change the format of smaller sets.  
The amount of space a set takes up depends on the element type of the  
set and the {$packset x} setting. Neither of these would automatically  
change for existing sets.

That said, sets for 256 elements already take up 32 bytes. Larger sets  
will usually be quite sparse, which means that just increasing the  
size will end up wasting a lot of memory. It would probably be better  
to use a dedicated bitmap class (generic or not) instead that is more  
clever than just using a bit array (although you could still do that  
in the class, using a bitpacked array of boolean).


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