Question

代码在

之下

class GraphicBase
{
    public:
        virtual void Print()=0;
        // for using with vtable polymorphism
        GraphicBase* Get() { return this; }
};


class Point: public GraphicBase
{
    public:
        Point( int, int ){}

        void Print() override { std::cout << "Point" << std::endl; }
        void PrintNonVirtual() { std::cout << "Point" << std::endl; }
};

class Line: public GraphicBase
{
    public:
        Line( Point, Point ){}
        void Print() override { std::cout << "Line" << std::endl; }
        void PrintNonVirtual() { std::cout << "Line" << std::endl; }
};


template < typename T >
class Graphics: public T
{
    public: 
        using T::T;

        // for using with variants
        T GetNonVirtual() { return static_cast<T>(*this);}
};  

Graphics( int, int ) -> Graphics<Point>;
Graphics( Point, Point ) -> Graphics<Line>;

int main()
{
    Graphics p1(1,1);
    Graphics l1({1,2},{3,4});

    // using vtable polymorphism
    std::vector<GraphicBase*> v;
    v.push_back( &p1 );
    v.push_back( &l1 );

    for ( auto el: v ) el->Print();

    // using the Get() to get the base pointer
    GraphicBase* ptr;
    ptr = p1.Get();
    ptr->Print();

    ptr = l1.Get();
    ptr->Print();

    // or using variants:
    using VT = std::variant< Point, Line >;

    std::vector<VT> var;
    var.push_back( p1 );
    var.push_back( l1 );

    for ( auto& el: var )
    {
        std::visit( []( auto& v ){ v.PrintNonVirtual(); }, el );
    }

    // here we get a copy of the object ( references not allowed in variants! )
    VT va1 = p1.GetNonVirtual();
    VT va2 = p1.GetNonVirtual();

    std::visit( []( auto& v ){ v.PrintNonVirtual(); }, va1 );
    std::visit( []( auto& v ){ v.PrintNonVirtual(); }, va2 );
 }

当我尝试运行程序时，Python突出显示第8行中的第一个a，并且它表示无效语法。我无法弄清楚代码有什么问题。如果你帮忙的话，非常感谢

Answer 1

更正代码：

i=0
a=0
Matrix=[1 for i in range(1000)]
while i<1000:
  Matrix[i]=(1/1000)*((i*(1/1000)))**2
  a=a+Matrix[i]
  i=i+1
print (a)

Python中变量的语法无效

1 个答案: