A class or pointer type
X
meets the requirements of an input iterator for the value type
T
if
X meets the *Cpp17Iterator* ([iterator.iterators]) and
*Cpp17EqualityComparable* (Table 28) requirements and
the expressions in Table 87 are valid and have
the indicated semantics.

In Table 87, the term
*the domain of ==*
is used in the ordinary mathematical sense to denote
the set of values over which
== is (required to be) defined.

This set can change over time.

Each algorithm places additional requirements on the domain of
== for the iterator values it uses.

Table 87: *Cpp17InputIterator* requirements (in addition to *Cpp17Iterator*) [tab:inputiterator]

Expression | Return type | Operational | Assertion/note | |

semantics | pre-/post-condition | |||

a != b | decltype(a != b) models boolean-testable | !(a == b) | ||

*a | reference, convertible to T | |||

a->m | (*a).m | |||

++r | X& | |||

(void)r++ | equivalent to (void)++r | |||

*r++ | convertible to T | { T tmp = *r; ++r; return tmp; } |