How can a vector name be treated as an array name?

Question

Firstly I am new to C++ so may be the question is stupid !! Secondly I have already seen the related answers to this and can conclude that name of a vector could be treated as an array.

vector <int> myVector(7,10);   // creates a vector of size 7 and initializes with 10

We may use the name myVector as an array and write like myVector[0], myVector[1]...

But since vector is a class and myVector is it's object there should be storage area inside that object which could be treated as an array like myVector.someArray[0], myVector.someArray[1] not the object name itself how does that become possible?

Okay, first forget Java. In C++ we have overloaded operators that are actually syntactic aliases for functions. The [] is such an operator. — Michael Chourdakis, Apr 22 '20 at 17:47
Are you thinking of `myVector.data()`? The `data` method gets you a pointer to the vectors internal storage area. — john, Apr 22 '20 at 17:48
Nitpick: `std::vector` is not a class. It's a class template. `std::vector` is a class. — Ted Lyngmo, Apr 22 '20 at 17:49
https://stackoverflow.com/questions/4421706/what-are-the-basic-rules-and-idioms-for-operator-overloading — Mat, Apr 22 '20 at 17:49
@MichaelChourdakis : So the [] operator is overloaded and internally the array is accessed ? — Kush, Apr 22 '20 at 18:06
Nitpick: in C++ basically everything that has a type is an object, including `int`, arrays and pointers. The only things that aren't are references and functions. — Caleth, Apr 22 '20 at 18:53
@Kush yes, `std::vector` overloads `operator[]` to access the internal array — Remy Lebeau, Apr 22 '20 at 20:36

Gerhard Stein · Answer 1 · 2020-04-24T07:11:27.557

very simple, overloaded operators:

operator overloading

When you define in your class these kinds of methods, you get to use those special operators; the ones which already can be used with primitive data types as the standard describes.

In case of vector you have something like

...

const Element& operator[](const unsigned int index)
{
     return internalArray[index];
}

...

within its class declaration.

Something similar you will find in the std::vector class, so you can even build your own vector class if you'd like to do that.

For clarification, if a class has the []-Operator defined, you can do something like this with its object:

vec[4];

which is equivalent to:

vec.operator[](4);

That also means the parameter of the overloaded operator can be chosen. You could even pass a string to the [] operator.

For example std::map does that very nicely:

std::map -> Check out the example

You [should probably](https://stackoverflow.com/a/4421719/4850111) provide a `const Element& operator[]` too. — nada, Apr 24 '20 at 07:06
@nada: Though not required, in this case better to do also for the parameter, you are right. Thank you! — Gerhard Stein, Apr 24 '20 at 07:12

How can a vector name be treated as an array name?

1 Answers1