toString of lambda expressions in c++?

Question

Is there any way to print a C++ lambda expression and see a textual representation of the function it represents? Here is a simple example showing what I mean:

#include <iostream>
#include <functional>

const char *toString(const std::function<int(int)> &f)
{
    // then a magic happens ...
    return "if (...) { ... }";
}
int main(int argc, char **argv)
{
    auto f1 = [=](int i){ if (i<5) {return 8*2;} else {return 2;} };
    auto f2 = [=](int i){ if (i>3) {return i*i;} else {return 7;} };
    std::cout << toString(f1) << "\n";
}

Any way to achieve this?

No, is the simple answer. What you are asking for seems equivalent to a disassembler for C++. Something that is impossible. — john, Apr 18 '20 at 08:36
You can write your lambda body in macro expression. But this is will be only string representation of code without resolving type, functions and etc. — Mister_Jesus, Apr 18 '20 at 08:39

score 1 · Accepted Answer · answered Apr 18 '20 at 09:17

No, there is not. C++ is a language without any kind of reflection. It's impossible to implement such function.

The possible workarounds include puting the lambda sources in a string literal in your program or for example reading the source file from your program.

toString of lambda expressions in c++?

1 Answers1