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From: tohava on 29 Oct 2009 05:17
On Oct 29, 1:13 am, PGK <graham.k...(a)gmail.com> wrote:
> My question is, can I reconfigure this code so that I don't have to
> explicitly specify the types of the two function pointers? For
> example, something "like": Loop2<2>::foo(f2,f1);

Just add this:
template<int N, typename BASE_FUNC, typename INDUCTIVE_FUNC>
void Repeat(BASE_FUNC bFunc, INDUCTIVE_FUNC iFunc) {
Loop2<BASE_FUNC, INDUCTIVE_FUNC, N>::foo(bFunc, iFunc);
}

Which can be called like this:
Repeat<2>(f2, f1);


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From: Paul Bibbings on 29 Oct 2009 15:27
PGK wrote:
> I've written a simple template metaprogramming loop (below) using a
> struct template which requires a loop index, and two function
> signatures; one for the base (zero) case, and one for the inductive
> (ith) case. As you can see below, I start things off with a call like
> this:
>
> Loop2<double (*)(double), void (*)(int), 2 >::foo(f2,f1);
>
> and the output is:
>
> Hello from f1(2).
> Hello from f1(1).
> Hello from f2(0.123).
>
> My question is, can I reconfigure this code so that I don't have to
> explicitly specify the types of the two function pointers? For
> example, something "like": Loop2<2>::foo(f2,f1);

You could provide a simple helper function that re-orders the template
parameters and uses template argument deduction to deduce the function pointers
for you. As, for example:

// ...

template<int i, typename BaseFunc, typename InductiveFunc>
void loop2_foo(BaseFunc bFunc, InductiveFunc iFunc)
{
Loop2<BaseFunc, InductiveFunc, i>::foo(bFunc, iFunc);
}

int main()
{
loop2_foo<2>(f2, f1);

// ...
}

Regards

Paul Bibbings

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