Programming Forums > Application Development > C++

codylee270 · Apr 19th, 2006, 8:36 PM

Hi all,

I actually thought I was gunna get this one on my own, but the text I was reading from is a little confusing int the inheritance deptartment and what to do with constructors of subclasses. Anyways, this is a program that is supposed to create and initialize a Rectangle object, and use its properties to create a Box object.

(Toggle Plain Text)

#include <iostream>
#include <iomanip>

using namespace std;     

class Rectangle
{
      protected:
                float length;
                float width;
      public:
                Rectangle(float, float);
                virtual float area(){return length*width;}
};

Rectangle::Rectangle(float l, float w)
{
      length = l;
      width = w;
}

class Box : public Rectangle
{
      protected:
                float depth;
      public:
                Box( float l, float w, float d):Rectangle(l), Rectangle(w), depth(d) {}
                virtual float area();
                float volume(){return length*width*depth;}
}
float Box::area() //overide rect. area, compute surface area
{
      return(4*(length*width)+2*(width*depth));
}
    

int main()
{
    Rectangle r1(2, 4);
    Box b1(2,4,6);
    cout << "The area of the Rectangle is : " << r1.area() << "." << endl;
    cout << "The surface area of the Box is : " << b1.area() << "." << endl;
    cout << "The volume of the Box is : " << b1.volume() << ".\n" << endl;
   
    system("PAUSE");
    return 0;

}

Even though i'm going to post the log of the errors from the compiler, I do believe all of the problems stem from the contructor of the Box object.

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Box( float l, float w, float d):Rectangle(l), Rectangle(w), depth(d) {}

I tried to do something similar to the book, but of course the compiler doesn't like it, and it doesn't give an example of making a constructor that ISN'T inline. So, 1) Could someone tell me how to make this work with the inline constructor? 2 ) How can you do this without having to do it inline.? 3) Why doesn't the subclass constructor have to have a semicolon after its declaration?

Errors

(Toggle Plain Text)

In constructor `Box::Box(float, float, float)':
multiple initializations given for base `Rectangle'
no matching function for call to `Rectangle::Rectangle(float&)'
note: candidates are: Rectangle::Rectangle(const Rectangle&)
note: Rectangle::Rectangle(float, float)

At global scope:
new types may not be defined in a return type
two or more data types in declaration of `area'
prototype for `Box Box::area()' does not match any in class `Box'
candidate is: virtual float Box::area()
`Box Box::area()' and `virtual float Box::area()' cannot be overloaded

In member function `Box Box::area()':
conversion from `float' to non-scalar type `Box' requested

Cache · Apr 19th, 2006, 11:29 PM

Pass the base class' constructor arguments exactly as they appear in the base class. And the derived class should have a semicolon at the end.

Inline constructor:

(Toggle Plain Text)

class Box : public Rectangle
{
protected:
	float depth;
public:
	Box( float l, float w, float d) : Rectangle(l, w), depth(d) {}
	float area();
	float volume(){return length*width*depth;}
};

Non-inline constructor (just take the initializer list with you):

(Toggle Plain Text)

class Box : public Rectangle
{
protected:
	float depth;
public:
	Box( float l, float w, float d);
	float area();
	float volume(){return length*width*depth;}
};

Box::Box( float l, float w, float d) : Rectangle(l, w), depth(d)
{
	// Blah!					
}

I imagine the base class constructor arguments need to be passed in the initializer list because of the order of instantiation -- the bass class constructor being called before the derived class.

Apr 19th, 2006, 8:36 PM	#1
codylee270 Unverified User Join Date: Sep 2005 Posts: 209 Rep Power: 0	Inheritance and polymorphism exercise problems, plus other questions Hi all, I actually thought I was gunna get this one on my own, but the text I was reading from is a little confusing int the inheritance deptartment and what to do with constructors of subclasses. Anyways, this is a program that is supposed to create and initialize a Rectangle object, and use its properties to create a Box object. (Toggle Plain Text) #include <iostream> #include <iomanip> using namespace std; class Rectangle { protected: float length; float width; public: Rectangle(float, float); virtual float area(){return lengthwidth;} }; Rectangle::Rectangle(float l, float w) { length = l; width = w; } class Box : public Rectangle { protected: float depth; public: Box( float l, float w, float d):Rectangle(l), Rectangle(w), depth(d) {} virtual float area(); float volume(){return lengthwidthdepth;} } float Box::area() //overide rect. area, compute surface area { return(4(lengthwidth)+2(widthdepth)); } int main() { Rectangle r1(2, 4); Box b1(2,4,6); cout << "The area of the Rectangle is : " << r1.area() << "." << endl; cout << "The surface area of the Box is : " << b1.area() << "." << endl; cout << "The volume of the Box is : " << b1.volume() << ".\n" << endl; system("PAUSE"); return 0; } #include <iostream> #include <iomanip> using namespace std; class Rectangle { protected: float length; float width; public: Rectangle(float, float); virtual float area(){return lengthwidth;} }; Rectangle::Rectangle(float l, float w) { length = l; width = w; } class Box : public Rectangle { protected: float depth; public: Box( float l, float w, float d):Rectangle(l), Rectangle(w), depth(d) {} virtual float area(); float volume(){return lengthwidthdepth;} } float Box::area() //overide rect. area, compute surface area { return(4(lengthwidth)+2(widthdepth)); } int main() { Rectangle r1(2, 4); Box b1(2,4,6); cout << "The area of the Rectangle is : " << r1.area() << "." << endl; cout << "The surface area of the Box is : " << b1.area() << "." << endl; cout << "The volume of the Box is : " << b1.volume() << ".\n" << endl; system("PAUSE"); return 0; } Even though i'm going to post the log of the errors from the compiler, I do believe all of the problems stem from the contructor of the Box object. (Toggle Plain Text) Box( float l, float w, float d):Rectangle(l), Rectangle(w), depth(d) {} Box( float l, float w, float d):Rectangle(l), Rectangle(w), depth(d) {} I tried to do something similar to the book, but of course the compiler doesn't like it, and it doesn't give an example of making a constructor that ISN'T inline. So, 1) Could someone tell me how to make this work with the inline constructor? 2 ) How can you do this without having to do it inline.? 3) Why doesn't the subclass constructor have to have a semicolon after its declaration? Errors (Toggle Plain Text) In constructor `Box::Box(float, float, float)': multiple initializations given for base `Rectangle' no matching function for call to `Rectangle::Rectangle(float&)' note: candidates are: Rectangle::Rectangle(const Rectangle&) note: Rectangle::Rectangle(float, float) At global scope: new types may not be defined in a return type two or more data types in declaration of `area' prototype for `Box Box::area()' does not match any in class `Box' candidate is: virtual float Box::area() `Box Box::area()' and `virtual float Box::area()' cannot be overloaded In member function `Box Box::area()': conversion from `float' to non-scalar type `Box' requested In constructor `Box::Box(float, float, float)': multiple initializations given for base `Rectangle' no matching function for call to `Rectangle::Rectangle(float&)' note: candidates are: Rectangle::Rectangle(const Rectangle&) note: Rectangle::Rectangle(float, float) At global scope: new types may not be defined in a return type two or more data types in declaration of `area' prototype for `Box Box::area()' does not match any in class `Box' candidate is: virtual float Box::area() `Box Box::area()' and `virtual float Box::area()' cannot be overloaded In member function `Box Box::area()': conversion from `float' to non-scalar type `Box' requested

Apr 19th, 2006, 11:29 PM	#2
Cache Hobbyist Join Date: Sep 2005 Posts: 266 Rep Power: 4	Pass the base class' constructor arguments exactly as they appear in the base class. And the derived class should have a semicolon at the end. Inline constructor: (Toggle Plain Text) class Box : public Rectangle { protected: float depth; public: Box( float l, float w, float d) : Rectangle(l, w), depth(d) {} float area(); float volume(){return lengthwidthdepth;} }; class Box : public Rectangle { protected: float depth; public: Box( float l, float w, float d) : Rectangle(l, w), depth(d) {} float area(); float volume(){return lengthwidthdepth;} }; Non-inline constructor (just take the initializer list with you): (Toggle Plain Text) class Box : public Rectangle { protected: float depth; public: Box( float l, float w, float d); float area(); float volume(){return lengthwidthdepth;} }; Box::Box( float l, float w, float d) : Rectangle(l, w), depth(d) { // Blah! } class Box : public Rectangle { protected: float depth; public: Box( float l, float w, float d); float area(); float volume(){return lengthwidthdepth;} }; Box::Box( float l, float w, float d) : Rectangle(l, w), depth(d) { // Blah! } I imagine the base class constructor arguments need to be passed in the initializer list because of the order of instantiation -- the bass class constructor being called before the derived class.

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Programming Forums > Application Development > C++

Inheritance and polymorphism exercise problems, plus other questions