Declaration Scope

[alexBB]

Hello there,

I am facing a problem of converting a large gnu fortran program that I've written myself to C++. I'm using g++ compiler in Ubuntu 14.04. I immediately noticed a bad feature that reminded me of the old Pascal days. If I want to use a class "A" in class "B" I must define class "A" before class "B" not after, otherwise I get an error: "A has not been defined in this scope."

Can anything be done to avoid that? I want to position classes in arbitrary order.

Thanks, - Alex

[MiiNiPaa]

There is no way to avoid that. C++ uses "single pass" translation which means when something is parsed, you must have all used entities declared. With proper program structure this usually is not a problem: each class resides in own header and implementation unit, so there is no "order" for classes.

[AbstractionAnon]

There is one way to partially avoid the problem which is to use forward class declarations.

class B;  // Forward declaration

class A
{  B *    p_b;
...
};

This only works for pointers or references. Does not work for direct declaration.

[alexBB]

Thank you guys.

- Alex