Why can't I define a function inside another function?

Question

This is not a lambda function question, I know that I can assign a lambda to a variable.

What\'s the point of allowing us to declare, but not define a function insid

Answer 1

In the example you give, void two(int) is being declared as an external function, with that declaration only being valid within the scope of the main function.

That's reasonable if you only wish to make the name two available within main() so as to avoid polluting the global namespace within the current compilation unit.

Example in response to comments:

main.cpp:

int main() {
  int foo();
  return foo();
}

foo.cpp:

int foo() {
  return 0;
}

no need for header files. compile and link with

c++ main.cpp foo.cpp 

it'll compile and run, and the program will return 0 as expected.