On 4/8/13, Kenneth Zadeck <zad...@naturalbridge.com> wrote:
> The other problem, which i invite you to use the full power of
> your c++ sorcery on, is the one where defining an operator so
> that wide-int + unsigned hwi is either rejected or properly
> zero extended. If you can do this, I will go along with
> your suggestion that the internal rep should be sign extended.
> Saying that constants are always sign extended seems ok, but there
> are a huge number of places where we convert unsigned hwis as
> the second operand and i do not want that to be a trap. I went
> thru a round of this, where i did not post the patch because i
> could not make this work. And the number of places where you
> want to use an hwi as the second operand dwarfs the number of
> places where you want to use a small integer constant.
You can use overloading, as in the following, which actually ignores
handling the sign in the representation.
class number {
unsigned int rep1;
int representation;
public:
number(int arg) : representation(arg) {}
number(unsigned int arg) : representation(arg) {}
friend number operator+(number, int);
friend number operator+(number, unsigned int);
friend number operator+(int, number);
friend number operator+(unsigned int, number);
};
number operator+(number n, int si) {
return n.representation + si;
}
number operator+(number n, unsigned int ui) {
return n.representation + ui;
}
number operator+(int si, number n) {
return n.representation + si;
}
number operator+(unsigned int ui, number n) {
return n.representation + ui;
}
If the argument type is of a template type parameter, then
you can test the template type via
if (std::is_signed<T>::value)
.... // sign extend
else
.... // zero extend
See http://www.cplusplus.com/reference/type_traits/is_signed/.
If you want to handle non-builtin types that are asigne dor unsigned,
then you need to add a specialization for is_signed.
--
Lawrence Crowl
