I recently started learning about stacks in C++. While looking at an example, I noticed they used the following:
void showstack(stack <int> s).
I was wondering what the <> did, and how is it different from just using int?
Asked
Active
Viewed 79 times
-1
H. Martin
- 55
- 7
-
5Looks like you need [a good C++ book](https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list), particularly the chapter about templates – Yksisarvinen Oct 12 '19 at 18:15
-
2Well, `stack int s` is a syntax error. That's one way they're different. – cdhowie Oct 12 '19 at 18:15
-
yes, my compiler did not like it when i removed the <> part. – H. Martin Oct 12 '19 at 18:26
4 Answers
4
What you are looking at are template parameters.
Basically, stack is a template, declared (in a simplified manner) like this:
template <class T>
class stack { /*...*/ };
Thus, stack is not a class, you cannot talk about a stack type. It will only become a type once the template parameter is specified; for example: stack<int> is a stack of integers in this case.
Victor
- 13,914
- 19
- 78
- 147
-
That makes sense, thanks. I could not find anything online about it, but now that i know what they are i will read about it. – H. Martin Oct 12 '19 at 18:27
-
I recommend starting with one of the books in [this list](https://stackoverflow.com/q/388242/1673776). You will get a much better view over the concepts of C++. C++ is the language that can do anything and everything :). Also, if you found my answer useful, please do not forget to mark it as accepted. – Victor Oct 12 '19 at 19:58
1
stack just like many other containers is templated. You need to specify the type of elements you are going to store in the container.
template<
class T, // this what you specified in your code
class Container = std::deque<T>
> class stack;
There is no stack compiled in your code until you use one with a type, like you did.
Oblivion
- 7,176
- 2
- 14
- 33
0
The <> are used for templates, which tell a class what kind of data to expect. You could replace int with string and you would have a stack of strings that way.
Cristian Osiac
- 71
- 2