boost函数:clamp、gather、hex、is_palindrome

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clamp:

template<typename T, typename Pred>   T const & clamp ( T const& val,     typename boost::mpl::identity<T>::type const & lo,     typename boost::mpl::identity<T>::type const & hi, Pred p )  {//    assert ( !p ( hi, lo ));    // Can't assert p ( lo, hi ) b/c they might be equal    return p ( val, lo ) ? lo : p ( hi, val ) ? hi : val;  }

简述：给定三个数，返回中间数（Pred默认使用std::less)。

示例：

    int foo = 23;    foo = boost::algorithm::clamp(foo, 1, 10);    cout << foo << endl;

gather:

template <    typename BidirectionalIterator,  // Iter models BidirectionalIterator    typename Pred>                   // Pred models UnaryPredicatestd::pair<BidirectionalIterator, BidirectionalIterator> gather         ( BidirectionalIterator first, BidirectionalIterator last, BidirectionalIterator pivot, Pred pred ){//  The first call partitions everything up to (but not including) the pivot element,//  while the second call partitions the rest of the sequence.    return std::make_pair (        std::stable_partition ( first, pivot, !boost::bind<bool> ( pred, _1 )),        std::stable_partition ( pivot, last,   boost::bind<bool> ( pred, _1 )));}

简述：将容器中满足pred函数要求的元素聚集到pivot的两边，并返回满足元素的区间迭代器。

stable_partition函数作用是依据pred函数将容器分为两部分(前一部分满足函数要求，后一部分不满足函数要求),且元素的相对位置不发生变化。

示例：

int arr[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};    auto range = boost::algorithm::gather(arr, arr + 10, arr + 4, isEven);    //13 0 2 4 6 8 5 7 9    for(auto i = 0; i < sizeof(arr) / sizeof(int); ++i)    {        cout << *(arr + i) << " ";    }    cout << endl;    //02 4 6 8    for(auto ite = range.first; ite != range.second; ++ite)    {        cout << *ite << " ";    }    cout << endl;

hex:

is_palindrome:

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