ex6_2.cpp

c++程序设计教材第二版书上即课后习题源代码

//【例6.2】矩阵运算：矩阵转置与矩阵相乘函数模板。下标作为参数传递。
#include <iostream>
#include <iomanip>
using namespace std;

template <typename T1,typename T2> void inverse(T1 *mat1,T2 *mat2,int a,int b);
template <typename T1,typename T2>void multi(T1 *mat1,T2 *mat2,T2 *result,int a,int b,int c);
template <typename T>void output(T *mat,char*s,int a,int b);

int main(){
    int middle[6][3], result[6][4];
    int matrix1[3][6]={8,10,12,23,1,3,5,7,9,2,4,6,34,45,56,2,4,6};   
    int matrix2[3][4]={3,2,1,0,-1,-2,9,8,7,6,5,4};
    char *s1="result";
	char *s2="middle";
	inverse(matrix1,middle,6,3);
     //显式：inverse<int[6],int[3]> (matrix1,middle,6,3);
    multi(middle,matrix2,result,6,3,4);
     //显式：multi <int[3],int[4]> (middle,matrix2,result,6,3,4); 
    output(matrix1,"matrix1",3,6);
	output(middle,s2,6,3);
	output(matrix2,"matrix2",3,4);
	output(result,s1,6,4);
	return 0;
}
template <typename T1, typename T2>void inverse(T1 *mat1,T2 *mat2,int a,int b){            
    int i,j;
    for (i=0;i<b;i++)
      for (j=0;j<a;j++)
        mat2[j][i]=mat1[i][j];
	  return;                                                      
}
template <typename T1,typename T2>void multi(T1 *mat1,T2 *mat2,T2 *result,int a,int b,int c){
	//二维数组的类型仅指其组成元素类型(一维数组),而与元素数量无关
	//如matrix2和result是同一类型，其元素同为整型4元素一维数组，尽管前者只有3个元素，后者有6个
    int i,j,k;
    for (i=0;i<a;i++){
      for (j=0;j<c;j++){
        result[i][j] = 0;
        for (k=0;k<b;k++)
          result[i][j]+=mat1[i][k]*mat2[k][j];
      }
    }
    return;
}
template <typename T>void output(T *mat,char *s,int a,int b){
    int i,j;
	cout<<s<<endl;
    for (i=0;i<a;i++){
      for (j=0;j<b;j++)
        cout<<setw(6)<<mat[i][j];
      cout<<endl;
    }
    return;                                                       
}