#include <iostream>
#include <string>
 
struct foo {
    foo(const char* file, int line) : FOO_A(*this), FOO_B(*this) {
        std::cout << file << ":" << line << '\n';
    }
 
    template <typename T>
    foo& op(T val, const char* str) {
        std::cout << str << "=" << val << " ";
        return *this;
    }
    foo& FOO_A;
    foo& FOO_B;
  };
 
#define FOO_A(x) FOO_OP(x, B)
#define FOO_B(x) FOO_OP(x, A)
#define FOO_OP(x, next) \
    op((x), #x).FOO_ ## next
 
#define FOO\
  if ( (false) )\
    ;\
  else foo(__FILE__, __LINE__).FOO_A 
 
int main() {
    // recursive macros, wooo
    std::string world = "world";
    FOO("hello")(world)(40 + 2)("blah")(14.5f)('x');
}

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