模板函数，模板类 定义，使用

/* 模板函数 */
/* minmax.h */
//#pragma interface  //新版gnu c++ 不需要此条语句

template //T是类型占位符,class 可以指任何数据类型
//不一定是指c++ 类
T max(T a, T b)
{
    if (a > b)
        return a;
    else
        return b;
}

template
    T min(T a, T b)
{
    if (a < b)
        return a;
    else
        return b;
}

/* tminmax.cpp */
#include
//#pragma implementation "minmax.h"
#include "minmax.h"

//using namespace std; //使用标准名空间会有重名错误

//instatiate template functions

template int min(int, int);
template double min(double, double);
template char min(char, char);

template int max(int, int);
template double max(double, double);
template char max(char, char);

int main()
{
    int i1 = 100, i2 = 200;
    double d1 = 3.14159, d2 = 9.87654;
    char c1 = 'A', c2 = 'z';

    cout << "max(i1, i2) == " << max(i1, i2) << endl;
    cout << "max(d1, d2) == " << max(d1, d2) << endl;
    cout << "max(c1, c2) == " << max(c1, c2) << endl;

    cout << "min(i1, i2) == " << max(i1, i2) << endl;
    cout << "min(d1, d2) == " << max(d1, d2) << endl;
    cout << "min(c1, c2) == " << max(c1, c2) << endl;

    return 0;
   
}



模板类的定义使用。。

/* db.h */
/*
*    模板类
*/
#include

using namespace std;

class DBError {
private:
    string msg;
public:
    DBError(const string &msg_arg):msg(msg_arg) { }
    const string &what()const { return msg; }
};

template
    class TDatabase {
private:
    T *rp;
    int num;
public:
    TDatabase(int n):num(n)
        { rp = new T[num]; }
    ~TDatabase()
        { delete []rp; }
    T &GetRecord(int recnum) throw (DBError);
};

template
    T &TDatabase < T >::GetRecord(int recnum) throw (DBError)
{
    if(0 <= recnum && recnum < num)
        return rp[recnum];
    else
        throw DBError("Bad record number");
}

/* tdb.cpp */
#include
#include
#include "db.h"

using namespace std;

//Type of objects to store in database
class TRecord {
private:
    string name;
public:
    TRecord():name(){ }
    TRecord(const string &s):name(s) { }
    void Assign(const string &s) { name = s; }
    const string & GetName()const { return name; }
};

int main()
{
    int m;                        //Record number index
    TDatabase *pdb;    //Pointer to db of TRecords
    pdb = new TDatabase(3); //create 3-record database
    //Assign record data
    pdb->GetRecord(0).Assign("George Washington");
    pdb->GetRecord(1).Assign("John Adams");
    pdb->GetRecord(2).Assign("Thomes JefferSon");
    //Display database contents
    for (m = 0; m <= 2; m++) {
        cout << m << ": ";
        cout << pdb->GetRecord(m).GetName() << endl;
        }

//prompt user for record numbers
for (;;) {
    cout << "Record number?(q to quit)";
    cin >> m;
    if ( !cin.good() ) break;
    try {
        TRecord &tr = pdb->GetRecord(m);
        cout << m << ": " << tr.GetName() << endl;
        }
    catch (DBError error) {
        cout << "* * * Error:" << error.what() << endl;
        }
    }
}