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order
Description
Returns a unique unsigned Integral Constant associated with the key Key in Sequence.
Header
#include <boost/mpl/order.hpp>
Parameters
| Parameter | Requirement | Description |
|---|---|---|
| Sequence | Associative Sequence | A sequence to query. |
| Key | Any type | The queried key. |
Expression semantics
For any Associative Sequence s, and arbitrary type key:
typedef order<s,key>::type n;
| Return type: | Unsigned Integral Constant. |
|---|---|
| Semantics: | If has_key<s,key>::value == true, n is a unique unsigned Integral Constant associated with key in s; otherwise, n is identical to void_. |
Complexity
Amortized constant time.
Example
typedef map< pair<int,unsigned>, pair<char,long> > m; BOOST_MPL_ASSERT_NOT(( is_same< order<m,int>::type, void_ > )); BOOST_MPL_ASSERT(( is_same< order<m,long>::type,void_> ));