STL算法中函数对象和谓词

一元函数对象例子：
//1普通类 重载 函数调用操作符
template <typename T>
void FuncShowElemt(T &t)  //普通函数 不能像 仿函数那样记录状态
{
    cout << t << " ";
};

void showChar(char &t)
{
    cout << t << " ";
}

//函数模板 重载 函数调用操作符
template <typename T>
class ShowElemt
{
public:
    ShowElemt()
    {
        n = 0;
    }
    void operator()(T &t)
    {
        n++;
        cout << t << " ";
    }
    void printCount()
    {
        cout << n << endl;
    }
public:
    int n;
};

//1 函数对象 基本使用
void main()
{
    int a = 100;
    FuncShowElemt<int>(a); //普通的函数调用

    ShowElemt<int> showElemt; //函数对象 
    showElemt(a); //函数对象调用 
}

一元谓词例子：
//1元谓词 例子
template <typename T>
class Isdiv
{
public:
    Isdiv(const T &divisor) //
    {
        this->divisor = divisor;
    }
    bool operator()(T &t)
    {
        return (t%divisor == 0);
    }
protected:
private:
    T divisor;
};

void main()
{
    vector<int> v2;
    for (int i=10; i<33; i++)
    {
        v2.push_back(i);
    }
    vector<int>::iterator it;
    int a = 4;
    Isdiv<int> mydiv(a);
    // _InIt find_if(_InIt _First, _InIt _Last, _Pr _Pred)   //返回的是迭代器
    it = find_if(v2.begin(), v2.end(), Isdiv<int>(4));
    if (it != v2.end())
    {
        cout << "第一个被4整除的数是：" << *it << endl;
    }
}

二元函数对象例子：
template <typename T>
struct SumAdd
{
    T operator()(T &t1, T &t2)
    {
        return t1 + t2;
    }
};

template <typename T>
void printE(T &t)
{
    for (vector<int>::iterator it = t.begin(); it!=t.end(); it++ )
    {
        cout << *it << " ";
    }
}

void printVector(vector<int> &v)
{
    for (vector<int>::iterator it = v.begin(); it!=v.end(); it++ )
    {
        cout << *it << " ";
    }
}

void  main()
{
    vector<int> v1, v2 ;
    vector<int> v3;
    v1.push_back(1);
    v1.push_back(2);
    v1.push_back(3);

    v2.push_back(4);
    v2.push_back(5);
    v2.push_back(6);

    v3.resize(10);

    //transform(v1.begin(), v1.end(), v2.begin(),v3.begin(), SumAdd<int>());
    /*
    template<class _InIt1,
    class _InIt2,
    class _OutIt,
    class _Fn2> inline
        _OutIt transform(_InIt1 _First1, _InIt1 _Last1,
        _InIt2 _First2, _OutIt _Dest, _Fn2 _Func)
    */
    vector<int>::iterator it = transform(v1.begin(), v1.end(), v2.begin(),v3.begin(), SumAdd<int>());
    cout << *it << endl;
    printE(v3);    
}

二元谓词例子：
void current(int &v)
{
    cout << v << " ";
}

bool MyCompare(const int &a, const int &b)
{
    return a < b;
}
void main()
{
    vector<int> v(10);

    for (int i=0; i<10; i++)
    {
        v[i] = rand() % 100;
    }

    for_each(v.begin(), v.end(), current);
    printf("\n");
    sort(v.begin(), v.end(), MyCompare );

    printf("\n");
    for (int i=0; i<10; i++)
    {
        printf("%d ", v[i]);
    }
    printf("\n");
}