C++ overloaded function pointer

Question

I am not able to get this to work:

template<class Input, class Output, class Index>
size_t pack(void (*copy)(Input, Input, Output),
            size_t N, Input input, Output output,
            const Index &index);

size_t K = pack(&std::copy<const double*,double*>,
                M, C.data().begin(), C_.data().begin(),
                index.host);

compiler message I get tells me that copy is not resolved, instead I get unresolved overloaded function type>.

what am I doing wrong? thank you

bummers, I found problem, std::copy returns output not void. Should I delete this question? — Anycorn
– Anycorn, Commented Jul 27, 2010 at 3:27
You can write then accept your own answer. Better than deletin'. — John Kugelman
– John Kugelman, Commented Jul 27, 2010 at 3:37

Anycorn · Accepted Answer · 2010-07-27 04:00:10Z

2

well, I missed return type of std::copy which is output iterator type.

Correct code :

template<class Input, class Output, class Index>
size_t pack(Output (*copy)(Input, Input, Output),
            size_t N, Input input, Output output,
            const Index &index);

answered Jul 27, 2010 at 4:00

Anycorn

51.8k45 gold badges173 silver badges267 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

GManNickG · Accepted Answer · 2010-07-27 04:09:03Z

1

You could make a design change. One might be make the return type a separate template parameter:

template<class R, class Input, class Output, class Index>
size_t pack(R (*copy)(Input, Input, Output),
            size_t N, Input input, Output output,
            const Index &index);

The return type is deduced (and subsequently ignored by your code.) The other option, which I would recommend, would be to accept any generic function type:

template<class CopyFunc, class Input, class Output, class Index>
size_t pack(CopyFunc func,
            size_t N, Input input, Output output,
            const Index &index);

This doesn't enforce any specific signature, and provides the most flexibility.

answered Jul 27, 2010 at 4:09

GManNickG

506k55 gold badges505 silver badges551 bronze badges

Collectives™ on Stack Overflow

C++ overloaded function pointer

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related