Thread: Beginner question using headers

Nevermind after looking at it again I figured out why. I still have to include int add( int x, int y) { return x + y; } in the HelloWorld.cpp file right? The tutorial didn't show this. IF thats why then whats the point of putting that other code in the header file when you could add int add( int x, int y) at the top of the HelloWorld.cpp file? Or I'm guessing you would...

Jacob Dixon wrote: One would be if I develop a C++ application using visual c++ 2008, is there a way for it to be converted to run on Mac OS X? Or do you have to write it over in a different IDE? If you don't use any Microsoft specific functions, you would be able to reuse the code, but you would still need to compile it using a compiler for the MAC. As for you second question, where is ...

The whole build process consists of a compilation process and a linking process. Including the header is for the compiler to figure out the signature of the function. The linker needs the actual definition of the function.

Superman, That was it, I never defined it. The tutorial just showed int add( int x, int y) , It never showed the rest. So when I put this in the add.h file: int add( int x, int y) { return x + y; } It worked perfectly. I should of known better Thanks for helping out!

in general, you should avoid putting code in a .H file. put this in the .C/.CPP: int add( int x, int y) { return x + y; } and put this in the .H: extern int add( int x, int y); that extern says "there is a function which looks like this, but is implemented somewhere else". that will satisfy the compiler. the linker will take care of the rest. the reason you don't want to ...

Ohhh! Ok I understand. I haven't got far into the tutorials just yet but I figure on down they line they will talk about extern and more of the best practices. Thanks guys

Chris Losinger wrote: about the only time you'll do implementation in a .H file is if the function is a class member function. Or you're doing a naked inline global function. And about the only time that happens (or should IMNSHO) in C++ programs are those places you need those pesky friend functions that there's just no way around.

Chris Losinger wrote: about the only time you'll do implementation in a .H file is if the function is a class member function. ... or it's a template class. modified on Sunday, November 8, 2009 3:21 PM

yep. i was counting that as part of the 'class member function' category.

Ah. Very good.