Input Iterators

Library:  Iterators

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• Description
• Key to Iterator Requirements
• Requirements for Input Iterators
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A read-only, forward moving iterator

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NOTE -- For a complete discussion of iterators, see the Iterators section of this reference.

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Iterators are a generalization of pointers that allow a C++ program to uniformly interact with different data structures. Input iterators are read-only, forward moving iterators that satisfy the requirements listed below.

The following key pertains to the iterator requirement descriptions listed below:

a and b	values of type X
n	value representing a distance between two iterators
u, Distance, tmp and m	identifiers
r	value of type X&
t	value of type T

The following expressions must be valid for input iterators:

X u(a)	copy constructor, u == a
X u = a	assignment, u == a
a == b, a != b	return value convertible to bool
*a	a == b implies *a == *b
++r	returns X&
r++	return value convertible to const X&
*r++	returns type T
a -> m	returns (*a).m

For input iterators, a == b does not imply that ++a == ++b.

Algorithms using input iterators should be single pass algorithms. That is, they should not pass through the same iterator twice.

The value of type T does not have to be an lvalue.

Iterators, Output Iterators

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 24.1.1