How to using opCmp

[Heromyth]

== Quote from Jesse Phillips (jessekphillips+d at gmail.com)'s article
> On Sat, 17 Dec 2011 14:06:48 +0000, Heromyth wrote:
> > I have defined a opCmp function to overload comparison operators, then
> > how can I use it correctly?
> >
> > I can use it like this:
> >    int b = t1.opCmp(info);
> > and is it right like this:
> >    int b = t1 < info;
> Consider the code more to the point of:
> int b = t1.opCmp(info);
> bool c = t1 < info;
That's it. Thanks, I got what I wanted.
Here is the modified test code:
// Test.d
import std.stdio;
import std.algorithm;
import std.range;
import std.array;

public class LogLevel
{
    @property public static LogLevel Trace()
    {
        if( m_Trace is null )
            m_Trace = new LogLevel("Trace", 0);
        return m_Trace;
    }
    private static LogLevel m_Trace;

    @property public static LogLevel Info()
    {
        if( m_Info is null )
            m_Info = new LogLevel("Info", 2);
        return m_Info;
    }
    private static LogLevel m_Info;


    private int ordinal;
    private string name;

	public override  int opCmp(Object o)
	{
		LogLevel level1 = cast(LogLevel) o;
		int result = 0;
		if( this.Ordinal > level1.Ordinal)
			result = 1;
		else
			result = -1;
		writefln("result == %d", result);
		return result;
	}


    @property package int Ordinal()
    {
        return this.ordinal;
    }


    private this(string name, int ordinal)
    {
        this.name = name;
        this.ordinal = ordinal;
    }
}


int main(string[] args)
{
    LogLevel t1 = LogLevel.Trace;
    LogLevel t2 = LogLevel.Trace;
    LogLevel info = LogLevel.Info;
	bool a = t1 == t2;
	writefln("a == %s", a);

	int b = t1.opCmp(info);
	writefln("b == %d", b);

	b = t1 < info;
	writefln("b == %d", b);

	bool c = t1 > info;
	writefln("c == %s", c);

	c = t1 < info;
	writefln("c == %s", c);

    return 0;
}

/*
a == true
result == -1
b == -1
result == -1
b == 1
result == -1
c == false
result == -1
c == true
*/