#include <iostream>#include <valarray> class Matrix{int dim;std::valarray<int> data;public:explicit Matrix(int dim,int init=0): dim{dim}, data(init, dim*dim){}void clear(int value=0){ data= value;}void identity(){ clear(); diagonal()=1;}int& operator()(int x,int y){return data[dim* y+ x];} std::slice_array<int> diagonal(){return data[std::slice(0, dim, dim+1)];} std::slice_array<int> secondary_diagonal(){return data[std::slice(dim-1, dim, dim-1)];} std::slice_array<int> row(std::size_t row){return data[std::slice(dim* row, dim,1)];} std::slice_array<int> column(std::size_t col){return data[std::slice(col, dim, dim)];}template<unsigned,unsigned>friendclass MatrixStack;}; template<unsigned dim=3,unsigned max=8>class MatrixStack{std::valarray<int> stack;unsigned count=0;public: MatrixStack(): stack(dim* dim* max){}void print_all()const{std::valarray<int> row(dim*count);for(unsigned r=0; r!= dim;++r)// screen row{ row= stack[std::gslice(r* dim,{count, dim},{dim* dim,1})];for(unsigned i=0; i!= row.size();++i)std::cout<< row[i]<<((i+1)% dim?" ":" │ ");std::cout<<'\n';}}void push_back(Matrixconst& m){if(count< max){ stack[std::slice(count* dim* dim, dim* dim,1)]= m.data[std::slice(0, dim* dim,1)];++count;}}}; int main(){constexprint dim=3; Matrix m{dim}; MatrixStack<dim,12> stack; m.identity(); stack.push_back(m); m.clear(1); m.secondary_diagonal()=3; stack.push_back(m); for(int i=0; i!= dim;++i){ m.clear(); m.row(i)= i+1; stack.push_back(m);} for(int i=0; i!= dim;++i){ m.clear(); m.column(i)= i+1; stack.push_back(m);} m.clear(); m.row(1)=std::valarray<int>{4,5,6}; stack.push_back(m); m.clear(); m.column(1)=std::valarray<int>{7,8,9}; stack.push_back(m); stack.print_all();}
