# bidirectional_iterator_tag

Category: iterators | Component type: type

### Description

`Bidirectional_iterator_tag` is an empty class: it has no member functions, member variables, or nested types. It is used solely as a "tag": a representation of the Bidirectional Iterator concept within the C++ type system. Specifically, it is used as a return value for the function `iterator_category`. `Iterator_category` takes a single argument, an iterator, and returns an object whose type depends on the iterator's category. `Iterator_category`'s return value is of type `bidirectional_iterator_tag` if its argument is a Bidirectional Iterator.

### Example

See `iterator_category`

### Definition

Defined in the standard header iterator, and in the nonstandard backward-compatibility header iterator.h.

### Template parameters

None.

### Model of

Assignable

### Type requirements

None.

### Public base classes

None.

### Members

None.

### New Members

None.

### Notes

### See also

`iterator_category`, Iterator Tags, `iterator_traits`, `output_iterator_tag`, `input_iterator_tag`, `forward_iterator_tag` `random_access_iterator_tag`

Copyright © 1999 Silicon Graphics, Inc. All Rights Reserved. TrademarkInformation