Question

So I just learned (thanks guys) about decltype. I now can write really nice vector templates that actually outperform valarrays(!):

template <typename T, typename U>
vector<decltype(T()*U())> operator*(const vector<T>& A, const vector<U>& B){
  vector<decltype(T()*U())> C = vector<decltype(T()*U())>(A.size());
  typename vector<T>::const_iterator a = A.begin();
  typename vector<U>::const_iterator b = B.begin();
  typename vector<decltype(T()*U())>::iterator c = C.begin();
  while (a!=A.end()){
    *c = (*a) + (*b);
    a++; b++; c++;
  }
  return C;
}  

Is it possible to make this kind of templating even more “meta”, in the sense that we allow the operator (“*”) itself to be a template parameter? I.e. have one single template definition that works for *, +, %, etc, where the appropriate operator op is used in *c = (*a) op (*b)?

I’m betting it is not, but it would be nice!

Answer 1

As you expected, this answer is “no.” 🙂

However, you can use the preprocessor to generate such functions:

#define OPERATOR_BLOB(optype) \
    vector<…> operator optype (…) { … }

OPERATOR_BLOB(*)
OPERATOR_BLOB(+)
…