Is there a way to switch member variable initalization based on a template parameter?
Some enable_if trick or something similar?
I could do something like this with a lambda call
template<bool A>
struct Test{
static constexpr int a = [](){
if constexpr(A) return 1; else return 2;}();
};
but this fails for my actual use case with a look up array (also tried with std:array)
template<bool A>
struct Test{
// A==true variant
static constexpr std::int8_t table[4] {1,2,3,4};
// A==false variant
//static constexpr std::int8_t table[4] {4,6,7,3};
You can indeed use a lambda that will return a std::array according to the value of A
#include <array>
#include <cstdint>
template<bool A>
struct Test {
static constexpr auto table = [] {
if (A) { return std::array<std::int8_t,4> {1,2,3,4}; }
else { return std::array<std::int8_t,4> {4,6,7,3}; }
}();
};
static_assert (Test<true> ::table == std::array<std::int8_t,4> {1,2,3,4});
static_assert (Test<false>::table == std::array<std::int8_t,4> {4,6,7,3});
int main() {}