这是上次PPT所应该讲述的代码内容。现在放上来，大家就应该清楚PPT未完成的部分所想要描述的技术了。PS：代码中还是有些没用的东西。
template <typename LeftExp, typename Op, typename RightExp>
struct Expression 
{
const LeftExp & left;
const RightExp & right;
Expression(const LeftExp & _l, const RightExp & _r) : left(_l), right(_r){}
double operator [] (int index) const {
return Op::eval(left[index], right[index]);
}
};
struct EPLUS {
static double eval(double a, double b) { return a+b;}
};
class Matrix
{
private:
int M,N;
double * element;
public:
Matrix(int m, int n): M(m),N(n) {
element = new double[M*N];
}
~Matrix(){
if (element) {
delete []element;
element = 0;
}
}
int getM() const { return M;}
int getN() const { return N;}
int getSize() const {return M*N;}
double & operator ()(int i, int j) const { return element[i*N+j]; }
double operator [](int index) const {return element[index]; }
template <typename Exp>
Matrix & operator = (Exp & exp) {
int size = M*N;
for (int i=0;i<size;i++) {
element[i] = exp[i];
}
return * this;
}
template <typename LeftExp, typename RightExp>
inline Expression<LeftExp,EPLUS, RightExp> operator + (const LeftExp & a, const RightExp & b) {
return Expression<LeftExp, EPLUS, RightExp>(a, b);
}
int main() {
const int M=3, N=4;
Matrix a(M,N), b(M,N), c(M,N);
{
for (int i=0;i<M;i++)
for (int j=0;j<N;j++) {
a(i,j) = i+j;
b(i,j) = i*j;
c(i,j) = 0;
}
}
c = a + b;
return 0;
}