Using a template for a stack implementation; "name followed by :: must be a class or namespace"

Question

stack.h

template <class DataType>
class Stack {
private:
    int * topPtr;
public:
    Stack();    //constructor; initializes top to nullptr
    void push();    //adds a node
    void pop();     //removes most recently added node
};

And stack.cpp thus far:

#include "stack.h"
//using namespace std;
template <class DataType>
Stack::Stack() {
    topPtr = nullptr;
}

It is the Stack:: that is underlined with the error "name followed by :: must be a class or namespace." If relevant, I am using VS Code.

I would just like to have a generic stack implementation, and I'm not sure why I'm getting this error? Thanks!

" I would just like to have a generic stack implementation" that is [`std::stack`](https://en.cppreference.com/w/cpp/container/stack) — 463035818_is_not_a_number, Feb 21 '20 at 17:06
What's wrong with [std::stack](https://en.cppreference.com/w/cpp/container/stack)? — Jesper Juhl, Feb 21 '20 at 17:07
Before you go any further … you cannot (usually) split up templates into .cpp and .h files. — ChrisMM, Feb 21 '20 at 17:08
Does this answer your question? [Splitting templated C++ classes into .hpp/.cpp files--is it possible?](https://stackoverflow.com/questions/1724036/splitting-templated-c-classes-into-hpp-cpp-files-is-it-possible) — Code-Apprentice, Feb 21 '20 at 17:08
@Code-Apprentice That would lead to a linker error, not a compiler error like the OP is paraphrasing. — NathanOliver, Feb 21 '20 at 17:09
sorry for being super picky, but questions are nice question when they actually contain a question. Most of us are no native english speakers, but I have the feeling you could do better than putting a `?` at the end of something that isnt a question. — 463035818_is_not_a_number, Feb 21 '20 at 17:09
@NathanOliver it sounds like the OP is getting an error in the IDE before even compiling. — Code-Apprentice, Feb 21 '20 at 17:12

score 1 · Answer 1 · answered Feb 21 '20 at 17:10

1

Syntax of out of class definition is:

template <class DataType>
Stack<DataType>::Stack() : topPtr{nullptr} {}
//    ^^^^^^^^

answered Feb 21 '20 at 17:10

Jarod42

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This works, thank you! Somehow I missed that syntax while looking at my reference. – mostly_tired Feb 21 '20 at 17:14
2

But as state in comment, you will probably have other issues as you put template definitions in cpp. – Jarod42 Feb 21 '20 at 17:16
So I should move the implementation to the header file; is that correct? – mostly_tired Feb 21 '20 at 17:46
Yes. template definitions should be inline. – HWilmer Feb 21 '20 at 17:57

Using a template for a stack implementation; "name followed by :: must be a class or namespace"

1 Answers1