u/MFHavaWG21|🇦🇹 NB|P2721|P3049|P3625|P3729|P3786|P3813|P421613d ago
polymorphic not being equality comparable is annoying, they could just have just forwarded the operator== to the underlying pointer and it handles it.
These types (indirect and polymorphic) model value semantics. Value comparing two type-erased objects that share a base makes no sense in that model...
also polymorphic requires more bytes than a copyable pointer 24 bytes vs 8 since the copy ctor and dtor have to be function pointers.
Can be easily compressed to 16B in case you build your own vtable. Unless the spec contains some unexpected blocker, you could even reduce that down to 8B with minimal effort.
These types (indirect and polymorphic) model value semantics. Value comparing two type-erased objects that share a base makes no sense in that model...
They could only provide == if the base has one.
Can be easily compressed to 16B in case you build your own vtable. Unless the spec contains some unexpected blocker, you could even reduce that down to 8B with minimal effort.
Wouldn't the 8 byte version require anothee indirection
9
u/MFHavaWG21|🇦🇹 NB|P2721|P3049|P3625|P3729|P3786|P3813|P421613d ago
They could only provide == if the base has one.
Ok... what does that do? Shape has no idea how to compare a Rectangle and a Triangle.
You could say: "Well, they can never be equal". Right, right, but what about my next fancy class Square?
That's a problem you'd essentially need open-multimethods to solve...
Wouldn't the 8 byte version require anothee indirection
Not necessarily, you can allocate the object and a (custom) vtable in one allocation.
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u/MFHava WG21|🇦🇹 NB|P2721|P3049|P3625|P3729|P3786|P3813|P4216 13d ago
These types (
indirectandpolymorphic) model value semantics. Value comparing two type-erased objects that share a base makes no sense in that model...Can be easily compressed to 16B in case you build your own vtable. Unless the spec contains some unexpected blocker, you could even reduce that down to 8B with minimal effort.