关于NOIP结构体内置函数的问题

struct Matrix{
	int v[siz][siz];
	int x,y;
	
	void clear(){memset(v,0,sizeof(v));}
	void Mmul(Matrix a,Matrix b)
	{
		clear();
		x=a.x,y=b.y;int c=a.y;
		for(int i=1;i<=x;++i){
			for(int j=1;j<=y;++j){
				for(int k=1;k<=c;++k){
					v[i][j]=(v[i][j]+(long long)a.v[i][k]*b.v[k][j])%MOD;
				}
			}
		}return;
	}
	
	Matrix Mpw(Matrix a,int b)
	{
		Matrix x;x.clear();
		x.x=x.y=a.x;for(int i=1;i<=x.x;++i) x.v[i][i]=1;
		while(b){
			if(b&1) x.Mmul(x,a);
			b>>=1;a.Mmul(a,a);
		}return x;
	}
}F,A;