Concept ForwardIterator

ForwardIterator

Description

A forward iterator is an iterator that can read through a sequence of values. It is multi-pass (old values of the iterator can be re-used), and can be either mutable (data pointed to by it can be changed) or not mutable.

An iterator represents a position in a sequence. Therefore, the iterator can point into the sequence (returning a value when dereferenced and being incrementable), or be off-the-end (and not dereferenceable or incrementable).

Refinement of

Associated types

value_type
```
std::iterator_traits<Iter>::value_type
```
The value type of the iterator

category

std::iterator_traits<Iter>::iterator_category

The category of the iterator

Notation

Iter: A type playing the role of iterator-type in the ForwardIterator concept.
i, j: Objects of type Iter
x: Object of type value_type

Type expressions

Category tag: category must be derived from std::forward_iterator_tag.

Valid expressions

Name	Expression	Type	Precondition	Semantics	Postcondition
Dereference	*i	const-if-not-mutable value_type &	`i` is incrementable (not off-the-end)
Member access	i->{member-name} (return type is pointer-to-object type)	const-if-not-mutable value_type *	`i` is incrementable (not off-the-end)
Preincrement	++i	Iter &	`i` is incrementable (not off-the-end)
Postincrement	i++	Iter	`i` is incrementable (not off-the-end)	Equivalent to `{Iter j = i; ++i; return j;}`	`i` is dereferenceable or off-the-end

Complexity

All iterator operations must take amortized constant time.

Invariants

Predecrement must return object: &i = &(++i)
Unique path through sequence: i == j implies ++i == ++j

Models

T *
std::hash_set<T>::iterator

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