CODEWITHSUNDEEP
c++stliterator
ramb0tn1k
ramb0tn1k

Reputation: 151

why iterator defining as a struct but not as class?

I've some little question about STL iterator implementation.

Upvotes: 3

Views: 518

Answers (4)

xxg1413
xxg1413

Reputation: 1

Like the best answer

class and struct is the same except the access.so use struct or class don't have many difference.

we know the C++ is include C

using struct seem simply and making a distinction between struct and class.

this is the define of iterator

struct output_iterator_tag{}
struct input_iterator_tag{}
struct forward_iterator_tag : public input_iterator_tag {};
struct bidirectional_iterator_tag : public forward_iterator_tag{}
struct random_accessl_iterator_tag : public bidirectional_iterator_tag{}

Upvotes: 0

juanchopanza
juanchopanza

Reputation: 227380

It is an implementation choice. class and struct are almost the same in C++, the difference being the default access specifiers and inheritance, which are private for class and public for struct. So if a type has little need for private data members it may make more sense to implement it as a struct. But you can have exactly the same type implemented as either:

struct Iterator : IteratorBase {
  SomeType x;
};

is exactly the same as

class Iterator : public IteratorBase{
 public:
  SomeType x;
};

Upvotes: 5

Luchian Grigore
Luchian Grigore

Reputation: 258558

This is defined in the standard, 24.2 which describes the <iterator> header, which are struct. This choice was probably made because iterators provide access to container elements and making them class would be useless, the only difference being that class has private access level by default, whereas struct has public access level.

So there were 2 choices if declaring iterators class instead of struct:

  • make all members public, which is useless since the same effect can be obtained by making it directly struct.
  • make getters, which would provide unnecessary overhead and abstraction.

Upvotes: 4

ForEveR
ForEveR

Reputation: 55887

Who says you that iterator is defined by struct? In standart there is nothing about it. Struct and class have only one difference - access to the elements as default. So, in struct by default access is public and in class by default access is private.

Upvotes: 0

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