/*C++类模板及参数类型的运行时判断(typeid)
*/#include <stdio.h>
#include <typeinfo>
#include <vector>
using namespace std;template<class T>
class Exercise
{public:typedef T Type;typedef vector < Type > VT;Exercise(int n);void Display();private:VT dv;
};template<class T>
Exercise<T>::Exercise(int n)
{T v;printf("type: %s\n", typeid(T).name());for(int i = 0; i < n; i++){v = 1.1 * (i+1);dv.push_back(v);}
}template<class T>
void Exercise<T>::Display()
{char fmt[2][10] = {"%d\t", "%.2f\t"};char *p = fmt[0];if(typeid(T) == typeid(double) || typeid(T) == typeid(float))p = fmt[1];for(typename vector<T>::iterator it = dv.begin(); it != dv.end(); it++){printf(p, *it);}printf("\n\n");
}int main()
{Exercise<double> ex1(5);ex1.Display();Exercise<float> ex2(5);ex2.Display();Exercise<int> ex3(5);ex3.Display();Exercise<long> ex4(5);ex4.Display();printf("\n");printf("%s\n", typeid(ex1).name());printf("%s\n", typeid(ex2).name());printf("%s\n", typeid(ex3).name());printf("%s\n", typeid(ex4).name());return 0;
}

makefile:

CC=g++
CFLAGS=
BIN=aa: a.cpp$(CC) $(CFLAGS) -o $@ $<clean:rm -f *.o $(BIN)

编译运行：

[zcm@t #66]$make
g++  -o a a.cpp
[zcm@t #67]$./a
type: d
1.10	2.20	3.30	4.40	5.50	type: f
1.10	2.20	3.30	4.40	5.50	type: i
1	2	3	4	5	type: l
1	2	3	4	5	8ExerciseIdE
8ExerciseIfE
8ExerciseIiE
8ExerciseIlE
[zcm@t #68]$