polymorphism

问题 I have read some possible article I could found on the internet on polymorphism . But I think I could not quite grasp the meaning of it and its importance. Most of the articles don't say why it is important and how I can achieve polymorphic behavior in OOP (of course in JavaScript). I can not provide any code example because I haven't got the idea how to implement it, so my questions are below: What is it? Why we need it ? How it works? How can I achieve this polymorphic behavior in

问题 I would like my boost::spirit-based parser to be able to parse a file, convert the parsed rules into different types, and emit a vector containing all of the matches it found. All of the types that are emitted as attributes should be inherited from a base type, for example: #include <boost/spirit/include/qi.hpp> #include <boost/fusion/adapt_struct.hpp> #include <boost/shared_ptr.hpp> #include <boost/foreach.hpp> struct CommandBase { virtual void commandAction() { std::cout << "This is a base

问题 I have a collection (or list or array list) in which I want to put both String values and double values. I decided to make it a collection of objects and using overloading ond polymorphism, but I did something wrong. I run a little test: public class OOP { void prova(Object o){ System.out.println("object"); } void prova(Integer i){ System.out.println("integer"); } void prova(String s){ System.out.println("string"); } void test(){ Object o = new String(" "); this.prova(o); // Prints 'object'!!

问题 I would like to know if @JsonTypeInfo annotation can be used for interfaces. I have set of classes which should be serialized and deserialized. Here is what I'm trying to do. I have two implementation classes Sub1 , Sub2 implementing MyInt . Some of the model classes have the interface reference for the implementation types. I would like to deserialize the objects based on polymorphism @JsonTypeInfo(use=JsonTypeInfo.Id.NAME, include=As.WRAPPER_OBJECT) @JsonSubTypes({ @Type(name="sub1", value

问题 I am not really proficient in Haskell, so this might be a very easy question. What language limitation do Rank2Types solve? Don't functions in Haskell already support polymorphic arguments? 回答1: Do not functions in Haskell already support polymorphic arguments? They do, but only of rank 1. This means that while you can write a function that takes different types of arguments without this extension, you can't write a function that uses its argument as different types in the same invocation.

问题 I have two classes Integer and Fraction and one abstract class Number . I am suppose to perform addtion operation by overloading + and also I need to check equality of values using overloading of == operator on these classes. Operations to be performed 1. Add Integer + Integer = Integer 2. Add Fraction + Fraction = Fraction 3. Add Integer + Fraction = Fraction I have been able to do 1st and 2nd operation but not able to do addition of integer and fraction. Below is the code snippet: Number.h

问题 I'm trying to understand how polymorphism, object slicing and pointers work in this block of code. I'm working in Visual Studio. #include <iostream> class Man { public: virtual void speak() { std::cout << "I'm a man." << "\n"; } private: }; class Soldier : public Man { public: virtual void speak() { std::cout << "I'm a soldier." << "\n"; } private: }; int main() { Man man1; Soldier soldier1; man1 = soldier1; std::cout << "Man1: "; man1.speak(); Man *man2 = new Man; Man *soldier2 = new Soldier

问题 I am trying to make a polymorphic vector using std::reference_wrapper for these classes: struct Int2TypeBase{ virtual void which(){ std::cout << "Int2TypeBase" << "\n";} }; template <int v> struct Int2Type : public Int2TypeBase { enum { value = v }; void which(){ std::cout << "Int2Type<" << value << ">""\n";} friend bool operator==(const Int2Type& lhs, const Int2Type& rhs){ return lhs.v == rhs.v; } }; Now I am trying to make use of std::reference_wrapper like this: int main(){ using namespace

问题 I am trying to make a polymorphic vector using std::reference_wrapper for these classes: struct Int2TypeBase{ virtual void which(){ std::cout << "Int2TypeBase" << "\n";} }; template <int v> struct Int2Type : public Int2TypeBase { enum { value = v }; void which(){ std::cout << "Int2Type<" << value << ">""\n";} friend bool operator==(const Int2Type& lhs, const Int2Type& rhs){ return lhs.v == rhs.v; } }; Now I am trying to make use of std::reference_wrapper like this: int main(){ using namespace

问题 I am sure that this question has been asked and answered before, but I am having trouble searching without the proper terminology. I have two unique structs A & B (not classes). My code uses functional overloading to treat the structs differently. I don't understand how to handle the declaration polymorphism. I apologize for a pseudocode example. if( flag ==1 ){ declare stuct A scoped to main } else{ declare stuct B scoped to main } The pseudo code above will not work since the declarations