Single Pass Range

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### Single Pass Range

##### Notation

`X` | A type that is a model of Single Pass Range.
`a` | Object of type X.

##### Description

A range `X` where `boost::range_iterator<X>::type` is a model of Single Pass Iterator.

##### Associated types

Iterator type | `boost::range_iterator<X>::type` | The type of iterator used to iterate through a Range's elements. The iterator's value type is expected to be the Range's value type. A conversion from the iterator type to the `const` iterator type must exist.
Const iterator type | `boost::range_iterator<const X>::type` | A type of iterator that may be used to examine, but not to modify, a Range's elements.

##### Valid expressions

The following expressions must be valid.

Name | Expression | Return type
--- | --- | ---
Beginning of range | `boost::begin(a)` | `boost::range_iterator<X>::type` if `a` is mutable, `boost::range_iterator<const X>::type` otherwise
End of range | `boost::end(a)` | `boost::range_iterator<X>::type` if `a` is mutable, `boost::range_iterator<const X>::type` otherwise

##### Expression semantics

Expression | Semantics | Postcondition
--- | --- | ---
`boost::begin(a)` | Returns an iterator pointing to the first element in the Range. | `boost::begin(a)` is either dereferenceable or past-the-end. It is past-the-end if and only if `boost::distance(a) == 0`.
`boost::end(a)` | Returns an iterator pointing one past the last element in the Range. | `boost::end(a)` is past-the-end.

##### Complexity guarantees

`boost::end(a)` is at most amortized linear time, `boost::begin(a)` is amortized constant time. For most practical purposes, one can expect both to be amortized constant time.

##### Invariants

Valid range | For any Range `a`, `[boost::begin(a),boost::end(a))` is a valid range, that is, `boost::end(a)` is reachable from `boost::begin(a)` in a finite number of increments.
Completeness | An algorithm that iterates through the range `[boost::begin(a),boost::end(a))` will pass through every element of `a`.

##### See also

Extending the library for UDTs

Implementation of metafunctions

Implementation of functions

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