C++ named requirements: LegacyRandomAccessIterator
A LegacyRandomAccessIterator is a LegacyBidirectionalIterator that can be moved to point to any element in constant time.
If a LegacyRandomAccessIteratorit
originates from a Container, then it
's value_type
is the same as the container's, so dereferencing (*it
) obtains the container's value_type
.
A pointer to an element of an array satisfies all requirements of LegacyRandomAccessIterator.
Requirements
The type It
satisfies LegacyRandomAccessIterator if
 The type
It
satisfies LegacyBidirectionalIterator
And, given

value_type
, the type denoted by std::iterator_traits<It>::value_type 
difference_type
, the type denoted by std::iterator_traits<It>::difference_type 
reference
, the type denoted by std::iterator_traits<It>::reference 
i
,a
,b
, objects of typeIt
or const It 
r
, an lvalue of typeIt

n
, an integer of typedifference_type
The following expressions must be valid and have their specified effects:
Expression  Return type  Operational semantics  Notes 

r += n 
It& 
difference_type m = n; if (m >= 0) while (m) ++r; else while (m++) r; return r; 

a + n

It 
It temp = a; return temp += n; 

r = n  It& 
return r += n;  The absolute value of n must be within the range of representable values of difference_type . 
i  n  It  It temp = i; return temp = n;  
b  a  difference_type 
return n; (see the precondition)  Precondition:
Postcondition:

i[n]  convertible to reference
 *(i + n)  
a < b  contextually convertible to bool  Equivalent to return b  a > 0;  Precondition:
Strict total ordering relation:

a > b  contextually convertible to bool  b < a  Total ordering relation opposite to a < b 
a >= b  contextually convertible to bool  !(a < b)  
a <= b  contextually convertible to bool  !(a > b) 
The above rules imply that LegacyRandomAccessIterator also implements LessThanComparable.
AmutableLegacyRandomAccessIterator is a LegacyRandomAccessIterator that additionally satisfies the LegacyOutputIterator requirements.
ConceptFor the definition of
where the expositiononly concept  (since C++20) 
Defect reports
The following behaviorchanging defect reports were applied retroactively to previously published C++ standards.
DR  Applied to  Behavior as published  Correct behavior 

LWG 299 (N3066)  C++98  the return type of a[n] was requiredto be convertible to const value_type&  the return type is required to be convertible to reference 
LWG 448  C++98  the return type of a[n] was requiredto be convertible to value_type  the return type is required to be convertible to const value_type&^{[1]} 
LWG 1079  C++98 
b  a was defined using a < b ,resulted in circular definition  removed a < b from the definition 
 LWG issue 299 was reopened after this resolution.
See also
(C++20)  specifies that a bidirectional_iterator is a randomaccess iterator, supporting advancement in constant time and subscripting(concept) 
Iterator library  provides definitions for iterators, iterator traits, adaptors, and utility functions 
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