error here can anyone help

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  1. #1
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    Oct 2008
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    error here can anyone help

    the question is
    Construct a class named Coord that contain two floating –point data member named xval and yval , which will be used to store the x and y values of a point in rectangular coordinates. The function member should include appropriate constructor and display functions and friend function named conv_pol (). The conv_pol() function should accept two floating point member that represent a point in polar coordinates and convert them into rectangular coordinates .
    and here's my coding..
    Code:
    #include<iostream>
    #include<cmath>
    using namespace std;
     
    
    
    class Coord
    
    {
    	friend Coord conv_pol( float ,float);
    private:
    float xval;
    float yval;
    
    public:
    	void print();
    
    	Coord(float,float);
    
    
    };
    
    Coord::Coord(float x,float y)
    {
    	xval = x;
    	yval = y;
    }
    
    
    void Coord::print()
    {
    	cout<<'('<<xval<<','<<yval<<')'<<endl;
    }
    
    Coord conv_pol(float x,float y)
    { 
       Coord temp;
       temp.xval = temp.yval*cos(temp.yval*3.142 /180);
       temp.yval = temp.yval*sin(temp.yval*3.142 /180);
       return temp;
     
    }
    int main()
    {
    	Coord a;
    	a=conv_pol(10,210);
    	a.print();
    
    
     return 0;
    }
    the error says no appropriate default constructor not initialized but then.. have already done Coord(float,float) which is the default constructor..
    i am confused on how to edit the constructor here..
    so what do i have to do??

  2. #2
    Kernel hacker
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    So, you only have a constructor that takes two float parameters. You need to either give those parameters default values, or have a second constructor with no parameters.

    Edit: Or you can pass two values to the constructor, e.g.:
    Code:
    Coord conv_pol(float x,float y)
    { 
       Coord temp(x, y);
       temp.xval = temp.yval*cos(temp.yval*3.142 /180);
       temp.yval = temp.yval*sin(temp.yval*3.142 /180);
       return temp;
     
    }
    Note that your current code is broken - you are using xval and yval, but they have not been assigned any value. With the above fix, it should do the right thing.

    Surely your 3.142 should be a constant named PI or pi?


    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    C++ Witch laserlight's Avatar
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    As a variation of matsp's theme, I propose that you make conv_pol() a non-friend function, and then just write:
    Code:
    Coord conv_pol(float x, float y)
    {
        return Coord(y * cos(y * 3.142 / 180), y * sin(y * 3.142 / 180));
    }
    Incidentally, I notice that x is not used... is that intended or a bug?
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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