Concat two `const char` string literals

Question

Is it possible to concat two string literals using a constexpr? Or put differently, can one eliminate macros in code like:

#define nl(str) str \         


        

Answer 1

A little bit of constexpr, sprinkled with some TMP and a topping of indices gives me this:

#include 

template struct seq{};
template
struct gen_seq : gen_seq{};
template
struct gen_seq<0, Is...> : seq{};

template
constexpr std::array concat(char const (&a1)[N1], char const (&a2)[N2], seq, seq){
  return {{ a1[I1]..., a2[I2]... }};
}

template
constexpr std::array concat(char const (&a1)[N1], char const (&a2)[N2]){
  return concat(a1, a2, gen_seq{}, gen_seq{});
}

Live example.

I'd flesh this out some more, but I have to get going and wanted to drop it off before that. You should be able to work from that.