c++ program with exceptions not working

Question

I've tried to write this simple code in MinGW, but every time i try to set x as a negative number, it shows the message "out of system bounds!!" and it should show "x is lower than 0". I just don't understand why it keeps showing only that message....

    #include <iostream>

    #define Max 80
    #define Min 20

    using namespace std;

    class Punct
    {
protected:
    int x,y;

public:
    class xZero{};
    class xOutOfSystemBounds{};

    Punct (unsigned a, unsigned b)
    {
        x=a;
        y=b;
    }

    unsigned Getx()
    {
        return x;
    }

    unsigned Gety()
    {
        return y;
    }

    void Setx( unsigned a )
    {
        if( a<0 )
            throw xZero();
                else
                if(( a>Max || a<Min ) && a>0 )
                    throw xOutOfSystemBounds();
                    else
                    x=a;
    }

    void Sety( unsigned a )
    {
        if( a<0 )
            throw xZero();
                else
                if( a>Max || a<Min )
                    throw xOutOfSystemBounds();
                    else
                    y=a;
    }
};

int main()
{
    Punct w(4,29);

    try
    {
        w.Setx(-2);
        cout<<"noul x:>"<<w.Getx()<<'\n';
    }

    catch( Punct::xZero )
    {
        cout<<"x is lower than 0"<<'\n';
    }

    catch( Punct::xOutOfSystemBounds )
    {
        cout<<"out of system bounds!!"<<'\n';
    }

    catch( ... )
    {
        cout<<"Expresie necunoscuta!"<<'\n';
    }

    system("PAUSE");
    return 0;
 }

Answer 1

void Setx( unsigned a ) takes argument as unsigned int . When you send a (signed) negative number, it gets converted to unsigned int , and becomes a large positive number (> Max ) . Hence xOutOfSystemBounds exception is thrown, instead of xZero . You have to change

void Setx( int a ){ ...}

Answer 2

That's because you're using an unsigned in your setter arguments which, by definition, has no negative values. Change it to int and it should behave as expected.