[fpc-pascal] Custom operators for non-record types
pascaldragon at googlemail.com
Mon Jul 2 09:54:19 CEST 2012
Am 02.07.2012 04:46, schrieb JC Chu:
> Do you have some inside information on the extra limitations regarding
> ordinal, floating point, and set types?
> As I understand, the only limitation on operator “overloading” should
> be that the operator do not have a default interpretation for the
> operands–result type combination.
> The modulus operator, for example, is certainly not defined by default
> as (Double, Double) → Double; but when I try to define it, the
> compiler says it’s an “[i]mpossible operator overload”. The same goes
> for logical operators on enumeration types. (Although each
> enumeration element has an underlying numerical value, it requires the
> use of Ord() or an explicit cast to convert it into a numerical type
> accepted by bitwise logical operators.)
The best source of information is the compiler source itself. The whole
logic that decides whether an operator is overloadable or not is located
in htypechk.pas, isoperatoracceptable and more imporantly also
isbinaryoperatoroverloadable. From what I see everything is forbidden
except what is written in there as an exception (and the ** operator
which is always allowed).
> Maybe I should start preparing for a bug report?
Maybe there were reasons to not allow them... You can of course prepare
a bug report or wait till one of the other developers who are more
experienced in FPC's overloading speak up.
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