To clear a error Error. Only assignment, call, increment, decrement, and new object expressions can be used as a statement

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C#

class space
{
    int x, y, z;
    public space(int a, int b, int c)
    {
        x = a;
        y = b;
        z = c;
    }
    public void display()
    {
        Console.WriteLine("" + x);
        Console.WriteLine("" + y);
        Console.WriteLine("" + z);
        Console.WriteLine();
    }
    public static space operator -(space s)
    {
        //return new space(-s.x, -s.y, -s.z); 
        s.x = -s.x;
        s.y = -s.y;
        s.z = -s.z;
        return s;
    }
}
static void Main()
{
    space s = new space(10,-50,32);
    Console.Write("s:");
    s.display();
    -s;
    Console.Write("s:");
    s.display();
    Console.ReadLine();
}

Posted 11-Nov-11 0:29am

ananth2012

Updated 11-Nov-11 0:31am

Slacker007

v2

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Slacker007 11-Nov-11 6:32am

Your question is incomplete. Please explain your question/situation in more detail please. Thanks.

4 solutions

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OriginalGriff · Answer 1 · 2011-11-11T00:45:00

The problme is as the error says:

C#

-s;

Only assignment, call, increment, decrement, and new object expressions can be used as a statement

"-s" is none of those - you would have to assign the value somewhere in order for it to be acceptable.

C#

space x = -s;
Console.Write("x:");
x.display();

BTW: It is very bad practice to affect the current item in a negation operator: it is not clear that that would occur. Think about it: does it happen when you do this:

C#

int i = 17;
int j = i + -i;

No, j is assigned zero. If the negation operator worked your way, then it would be assigned -34, probably...
Use the commented out version to return a new instance instead.

UJimbo · Answer 2 · 2011-11-11T00:42:00

Solution 1

change your main function like this:

static void Main(string[] args)
{
   space s = new space(10, -50, 32);
   Console.Write("s:");
   s.display();
   s = -s;
   Console.Write("s:");
   s.display();
   Console.ReadLine();
}

Posted 11-Nov-11 0:42am

UJimbo

Tejas Vaishnav · Answer 3 · 2011-11-11T00:42:00

What you trying to do with over loading a - operator....

you use a minus operator to over load and use that for the task looks like to decrement operator perform..

you need to use a minus operator for performing only subtrac activity....
and if you want to perform decrement then use decrement operator to over load...

like this,,,,

C#

class space
{
    int x, y, z;
    public space(int a, int b, int c)
    {
        x = a;
        y = b;
        z = c;
    }
    public void display()
    {
        Console.WriteLine("" + x);
        Console.WriteLine("" + y);
        Console.WriteLine("" + z);
        Console.WriteLine();
    }
    public static space operator --(space s) // use decrement operator to over load....
    {
        //return new space(-s.x, -s.y, -s.z); 
        s.x = -s.x;
        s.y = -s.y;
        s.z = -s.z;
        return s;
    }
}
class Program
{
    static void Main(string[] args)
    {
        space s = new space(10, -50, 32);
        Console.Write("s:");
        s.display();
        --s;  // decrement operator used like this....
        // or if you want to over load your minus operator then use like this...
       // s = - s;
        Console.Write("s:");
        s.display();
        Console.ReadLine();
    }
}

see this for operator over loading...
http://www.csharp-station.com/Tutorials/Lesson18.aspx[^]

Wayne Gaylard · Answer 4 · 2011-11-11T00:43:00

Solution 3

You are going to have to put s = -s; (I take it this is what you mean). You cannot put -s; on it's own in the main function.

Posted 11-Nov-11 0:43am

Wayne Gaylard

To clear a error Error. Only assignment, call, increment, decrement, and new object expressions can be used as a statement

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