Am 31.12.2020 um 17:26 schrieb Gabor Boros via fpc-pascal:
Hi All,
I try to convert some C++ source to FPC, see below a short example
from it. How can I define same operator with FPC trunk?
class Cla
{
INT64 Num;
public:
Cla operator +(const Cla& m)
{
Cla ret(this);
ret.Num += m.Num;
return ret;
}
Depending on the usecase of that class it might be better to declare it
as a record, then you can declare the operator as an operator in Pascal
as well (in C++ class and struct are rather interchangeable with the
main difference being the default visibility (private for class and
public for struct)):
=== code begin ===
// interface section
type
Cla = record
Num: Int64;
class operator + (const aLeft, aRight: Cla): Cla;
end;
// implementation section
class operator Cla.+(const aLeft, aRight: Cla): Cla;
begin
Result := Default(Cla);
Result.Num := aLeft.Num + aRight.Num;
end;
=== code end ===
Otherwise you need to declare a global operator overload (which will not
work with generics):
=== code begin ===
// in interface section
operator + (aLeft, aRight: TCla): TCla;
// in implementation section
operator +(aLeft, aRight: TCla): TCla;
begin
Result := TCla.Create;
Result.Num := aLeft.Num + aRight.Num;
end;
=== code end ===
Please note that in both cases the operators in Pascal are static
functions, not member methods.
Regards,
Sven
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