Concept InputIterator

Description

An input iterator is an iterator that can read through a sequence of values. It is single-pass (old values of the iterator cannot be re-used), and read-only.

An input 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 (not necessarily what *i returns)
difference_type
```
std::iterator_traits<Iter>::difference_type
```
The difference 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 InputIterator concept.
i, j: Objects of type Iter
x: Object of type value_type

Type expressions

Category tag: category must be derived from std::input_iterator_tag, a model of DefaultConstructible, and a model of CopyConstructible.
Value type copy constructibility: value_type must be a model of CopyConstructible.
Difference type properties: difference_type must be a model of SignedInteger.

Valid expressions

Name	Expression	Type	Precondition	Semantics	Postcondition
Dereference	*i	Convertible to value_type	`i` is incrementable (not off-the-end)
Preincrement	++i	Iter &	`i` is incrementable (not off-the-end)
Postincrement	i++		`i` is incrementable (not off-the-end)	Equivalent to `(void)(++i)`	`i` is dereferenceable or off-the-end
Postincrement and dereference	*i++	Convertible to value_type	`i` is incrementable (not off-the-end)	Equivalent to `{value_type t = *i; ++i; return t;}`	`i` is dereferenceable or off-the-end

Complexity

All iterator operations must take amortized constant time.

Models

std::istream_iterator

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