What does it mean when we use a variable in C++ like a function with a default value as its parameter?

Question

I was reading a C++ code line. I encountered a weird code line where a variable was used as a function with a 0 as its parameter!

template <class T> class Stack {
    T data[50];
    int nElements;
public:
//This line is where the variable was used like a function!
    Stack() : nElements(0){}
    void push(T elemen);
    T pop();
    int tamanho();
    int isEmpty();
};

So what does exactly mean when we have: the constructor : private variable (0){}

This code line was very weird for me! Thanks

If you scroll a bit into the accepted answer to "A better way would be for B's constructor to directly call A's constructor in the initializer list..." you can see a discussion and some examples that should answer your question. — mattsilver, Apr 24 '15 at 17:31
Amir, you'll need to read your C++ text book. This is basic C++. — Mark Lakata, Apr 24 '15 at 17:31
@MarkLakata Such comments are best accompanied by [this link](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list). — Angew is no longer proud of SO, Apr 24 '15 at 17:34
Here's another one: http://stackoverflow.com/questions/1711990/what-is-this-weird-colon-member-syntax-in-the-constructor — chris, Apr 24 '15 at 17:34

score 2 · Answer 1 · answered Apr 24 '15 at 17:28

2

This is called an initializer list

answered Apr 24 '15 at 17:28

Buddy

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Pixelchemist · Accepted Answer · 2015-04-24T17:31:27.177

2

In the initializer_list of Stacks constructor, class member nElements is initialized with a value of zero upon creation of each Stack object.

The value 0 does not have any special meaning here, other than setting the initial number of elements for the Stack to zero as soon as it gets created and is empty.

edited Apr 24 '15 at 17:31

answered Apr 24 '15 at 17:29

Pixelchemist

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score 1 · Answer 3 · answered Apr 24 '15 at 17:29

1

This is called an 'initializer'. It is saying to initialize the variable with the given value, and the {} indicates the body of the constructor is empty.

answered Apr 24 '15 at 17:29

The other other Alan

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What does it mean when we use a variable in C++ like a function with a default value as its parameter?

3 Answers3