angelbeats's blog

By angelbeats, history, 3 years ago, In English
namespace std {
void debug_out() { cerr << endl; }
template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << to_string(H);
    debug_out(T...);
}
#ifdef LOCAL
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]: ", debug_out(__VA_ARGS__)
#define tee(...) [](const auto& x){ cerr << "[" << #__VA_ARGS__ << "]: "; debug_out(x); return x; }(__VA_ARGS__)
#else
#define dbg(...) do {} while(0)
#define tee(...) (__VA_ARGS__)
#endif
}

The code above introduces tee, which simply prints one value and returns it.

g++ -DLOCAL -O2 --std=c++17 -o a a.cpp

Don't use c++11. Don't change std to other names. You can get rid of the std wrapper.

And here's the complete version, which handles tuple of any length, as well as complex.

Complete version
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