Programming Forums > Application Development > C++

King · Feb 1st, 2007, 6:43 PM

I just have a few questions about templates. I will just use the following class as an example to use for my questions:

template <class T>
class MyClass
{
public:
	MyClass() {};
	~MyClass() {};
	void MyFunction(const T &);
};

template<class T>
void MyClass<T>::MyFunction(const T &value)
{
	// do something
}

Usually when I write a class I would put the implementation of the functions in a separate .cpp file, but when I do this I get compile errors. But if I put the implementation of the function in the same file as the class definition it works fine, why is that?
My second question is if I have to keep the implementation of my functions in the same file, would there be a point to still define it outside if the class definition like I have shown above, or should I just define it inside the class?
Thanks.

Eoin · Feb 1st, 2007, 8:01 PM

Too tired to phrase an intelligent answer to the first but this link seems to do a good job at explaining the details.

On the second question, well for your example it is largely just a matter of taste, but again the mentioned link goes more into the specifics.

bl00dninja · Feb 2nd, 2007, 2:44 AM

can't give any cool details...BUT i've been told that when you use templates the declarations and definitions need to be in one file.

the reason you find weird shit like this is that C++ is not a ground-up new language. it's a wrapper for C. so add-on crap like templates involves weird shit so they don't have to rewrite the whole compiler.

you just gotta live with it.

good luck!

King · Feb 3rd, 2007, 7:30 PM

Thanks for the info guys. Is there any difference at all if I define the function inline or outside of the class definition?

Feb 1st, 2007, 6:43 PM	#1
King Professional Programmer Join Date: Jan 2006 Location: Ontario, Canada Posts: 368 Rep Power: 0	Template Questions I just have a few questions about templates. I will just use the following class as an example to use for my questions: (Toggle Plain Text) template <class T> class MyClass { public: MyClass() {}; ~MyClass() {}; void MyFunction(const T &); }; template<class T> void MyClass<T>::MyFunction(const T &value) { // do something } template <class T> class MyClass { public: MyClass() {}; ~MyClass() {}; void MyFunction(const T &); }; template<class T> void MyClass<T>::MyFunction(const T &value) { // do something } Usually when I write a class I would put the implementation of the functions in a separate .cpp file, but when I do this I get compile errors. But if I put the implementation of the function in the same file as the class definition it works fine, why is that? My second question is if I have to keep the implementation of my functions in the same file, would there be a point to still define it outside if the class definition like I have shown above, or should I just define it inside the class? Thanks. __________________ I am Addicted to Linux!

Feb 1st, 2007, 8:01 PM	#2
Eoin Hobbyist Programmer Join Date: Jun 2006 Location: Ireland Posts: 152 Rep Power: 3	Too tired to phrase an intelligent answer to the first but this link seems to do a good job at explaining the details. On the second question, well for your example it is largely just a matter of taste, but again the mentioned link goes more into the specifics. __________________ Visit my website BinaryNotions.

Feb 2nd, 2007, 2:44 AM	#3
bl00dninja Programming Guru Join Date: Oct 2004 Location: namespace std Posts: 1,246 Rep Power: 5	can't give any cool details...BUT i've been told that when you use templates the declarations and definitions need to be in one file. the reason you find weird shit like this is that C++ is not a ground-up new language. it's a wrapper for C. so add-on crap like templates involves weird shit so they don't have to rewrite the whole compiler. you just gotta live with it. good luck! __________________ i put on my robe and wizard hat... Have you ever heard of Plato, Aristotle, Socrates?...Morons.

Feb 3rd, 2007, 7:30 PM	#4
King Professional Programmer Join Date: Jan 2006 Location: Ontario, Canada Posts: 368 Rep Power: 0	Thanks for the info guys. Is there any difference at all if I define the function inline or outside of the class definition? __________________ I am Addicted to Linux!

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Programming Forums > Application Development > C++

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