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POHow to return a reference in C++
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4633767
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2011-01-08T12:08:52.157
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2011-01-08T14:26:27.923
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If for example I create a new object in a function and I want to return its reference how can I do it? Lets say I got an IntClass that has a 'int num' field in the private. So i want to create a new element of IntClass in the function and return the reference of that object. I've tried something like that but it seems illegal (from some reason when I do such thing the Binaries gets deleted when I compile the code although I get no errors from the compiler itself (ECLIPSE): <pre><code> IntClass* a = new IntClass(10); IntClass &ref = *a; return ref; </code></pre> Any ideas how to return a reference then? EDIT: It's allowed to "assume" that C++ uses a Garbage-Collection As it's not clear to most of you WHY I "want" to do it so here is the full question: I got this file (Not made by me and can't be edited): poly_subtype.h: <pre><code>#ifndef POLY_SUBTYPE_H #define POLY_SUBTYPE_H #include <iostream> #include "cpu_add.h" using std::cout; using std::endl; //Deriving classes definition class IntClass; class DoubleClass; //The Virtual Number Class. IntClass and FloatClass will derive from this class. class Number { public: //return a Number object that's the results of x+this, when x is DoubleClass virtual Number& addDouble(DoubleClass& x) = 0; //return a Number object that's the results of x+this, when x is IntClass virtual Number& addInt(IntClass& x) = 0; //return a Number object that's the results of x+this, when x is either //IntClass or DoubleClass virtual Number& operator+(Number& x) = 0; //Print the number stored in the object virtual void print_number() = 0; }; class IntClass : public Number { private: int my_number; public: //Constructor IntClass(int n):my_number(n) {} //returns the number stored in the object int get_number() {return my_number;} //print the number stored in the object void print_number() {cout << my_number << endl;} //return a DoubleClass object that's the result of x+this Number& addDouble(DoubleClass& x); //return an IntClass object that's the result of x+this Number& addInt(IntClass& x); //return a Number object that's the result of x+this. //The actual class of the returned object depends on x. //If x is IntClass, then the result if IntClass. //If x is DoubleClass, then the results is DoubleClass. Number& operator+(Number& x); }; class DoubleClass : public Number { private: double my_number; public: //Constructor DoubleClass(double n):my_number(n) {} //returns the number stored in the object double get_number() {return my_number;} //Print the number stored in the object void print_number() {cout << my_number << endl;} //return a DoubleClass object that's the result of x+this Number& addDouble(DoubleClass& x); //return a DoubleClass object that's the result of x+this Number& addInt(IntClass& x); //return a DoubleClass object that's the result of x+this. //This should work if x is either IntClass or DoubleClass Number& operator+( Number& x); }; #endif </code></pre> and I've got this file (again, not written by me and can't be edited - says I can use those functions but not the '+' operator. cpu_add.h: <pre><code>#ifndef CPU_ADD_H #define CPU_ADD_H double add_double_double(double a, double b) {return (a+b);} double add_int_double(int a, double b) {return ((double)(a)+b);} int add_int_int(int a, int b) {return (a+b);} #endif </code></pre> My goal is to implement the next functions (which you can find their declarations and functionality in poly_subtype.h above): <pre><code>Number& IntClass::addInt(IntClass& x); Number& IntClass::addDouble(DoubleClass& x); Number& IntClass::operator+(Number& x); Number& DoubleClass::addInt(IntClass& x); Number& DoubleClass::addDouble(DoubleClass& x); Number& DoubleClass::operator+(Number& x); </code></pre> I hope it's more clear now. For example, AddInt: <pre><code>Number& IntClass::addInt(IntClass& x){ int num = add_int_int(my_number, x.get_number()); IntClass* a = new IntClass(num); IntClass &ref = *a; return ref; } </code></pre>
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How to return a reference in C++
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