| .. Iterators/Iterator Metafunctions//prior |40 |
| |
| prior |
| ===== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Iterator |
| > |
| struct prior |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns the previous iterator in the sequence. |Note:| ``prior`` has a number of |
| overloaded meanings, depending on the type of its argument. For instance, |
| if ``X`` is an |Integral Constant|, ``prior<X>`` returns an decremented |
| |Integral Constant| of the same type. The following specification is |
| iterator-specific. Please refer to the corresponding concept's |
| documentation for the details of the alternative semantics |-- end note|. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/next_prior.hpp> |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+---------------------------+-----------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===========================+===================================+ |
| | ``Iterator`` | |Bidirectional Iterator|. | An iterator to decrement. | |
| +---------------+---------------------------+-----------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Bidirectional Iterator|\ s ``iter``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef prior<iter>::type j; |
| |
| :Return type: |
| |Bidirectional Iterator|. |
| |
| :Precondition: |
| ``iter`` is decrementable. |
| |
| :Semantics: |
| ``j`` is an iterator pointing to the previous element in the sequence. |
| If ``iter`` is a user-defined iterator, the library-provided default |
| implementation is equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef iter::prior j; |
| |
| |
| Complexity |
| ---------- |
| |
| Amortized constant time. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef vector_c<int,1> v; |
| typedef begin<v>::type first; |
| typedef end<v>::type last; |
| |
| BOOST_MPL_ASSERT(( is_same< prior<last>::type, first > )); |
| |
| |
| See also |
| -------- |
| |
| |Iterators|, |begin| / |end|, |next|, |deref| |
| |
| |
| .. copyright:: Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
