static inline T op2_impl(Op op, T x, T y) {
switch (op) {
case OP_ADD: return add_impl(x, y);
case OP_SUB: return sub_impl(x, y);
case OP_MUL: return mul_impl(x, y);
case OP_DIV: return div_impl(x, y);
case OP_POW: return pow_impl(x, y);
default: throw std::invalid_argument("Wrong number of arguments for operator");
}
}
constexpr T pow_impl(T base, T exp, T result = 1) {
return exp == 1 ?
base*result :
pow_impl(base*base, exp/2, exp%2 ? result*base : result);
}
