compile time loops

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I would like to know if it is possible to have sort of compile time loops.
For example, I have the following templated class:

template<class C, int T=10, int B=10>
class CountSketch
{
public:
    CountSketch()
    {   
         hashfuncs[0] = &CountSketch<C>::hash<0>;
         hashfuncs[1] = &CountSketch<C>::hash<1>;
         // ... for all i until i==T which is known at compile time
    };
private:
    template<int offset>
    size_t hash(C &c)
    {
        return (reinterpret_cast<int>(&c)+offset)%B;
    }
    size_t (CountSketch::*hashfuncs[T])(C &c);
};

I would thus like to know if I can do a loop to initialize the T hash functions using a loop. The bounds of the loops are known at compile time, so, in principle, I don't see any reason why it couldn't be done (especially since it works if I unroll the loop manually).

Of course, in this specific example, I could just have made a single hash function with 2 parameters (although it would be less efficient I guess). I am thus not interested in solving this specific problem, but rather knowing if "compile time loops" existed for similar cases.

Thanks!

templates c++
6 Answers

with C++20 and consteval compile time loops became possible without doing template hell unless the value can have multiple types:

consteval int func() {
    int out = 0;
    for(int i = 10; i--;) out += i;
    return out;
}
int main() {
    std::cout << func(); // outputs 45
}
user_148720860
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