c++类模板及参数类型的运行时判断

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/*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]$makeg++  -o a a.cpp[zcm@t #67]$./atype: d1.102.203.304.405.50type: f1.102.203.304.405.50type: i12345type: l123458ExerciseIdE8ExerciseIfE8ExerciseIiE8ExerciseIlE[zcm@t #68]$