digitalmars.D.learn - How to using opCmp
- Heromyth (90/90) Dec 17 2011 I have defined a opCmp function to overload comparison operators, then h...
- bearophile (4/6) Dec 17 2011 I don't have an answer yet, but I suggest you to look at the D docs that...
- Heromyth (15/21) Dec 17 2011 describe how to use opCmp. Probably you need to accept a const Object, a...
- Manfred_Nowak (7/13) Dec 17 2011 Nothing because the call of the operator `<' interprets the result of th...
- Jesse Phillips (4/11) Dec 17 2011 Consider the code more to the point of:
- Heromyth (75/86) Dec 17 2011 That's it. Thanks, I got what I wanted.
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;
In my test code, I get different value for b. What can I do?
Thanks for helps.
//=============
//Test code:
//=============
import std.stdio;
import std.conv;
import std.file;
import std.algorithm;
import std.range;
import std.array;
import std.format;
import std.path;
import std.ascii;
import std.utf;
import std.process;
public final 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;
public string getName()
{
return name;
}
private int ordinal;
private string name;
public static LogLevel FromString(string levelName)
{
if (levelName.empty())
{
throw new Exception("levelName");
}
return Trace;
}
public int opCmp(LogLevel level1)
{
int result = 0;
if( this.Ordinal > level1.Ordinal)
result = 1;
else if( this.Ordinal == level1.Ordinal)
result = 0;
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;
int a = t1 > t2;
writefln("a == %d", a);
int b = t1.opCmp(info);
writefln("b == %d", b);
b = t1 < info;
writefln("b == %d", b);
b = t1 > info;
writefln("b == %d", b);
return 0;
}
//=============
Dec 17 2011
Heromyth:I have defined a opCmp function to overload comparison operators, then how can I use it correctly?I don't have an answer yet, but I suggest you to look at the D docs that describe how to use opCmp. Probably you need to accept a const Object, and to use override. I suggest to strip your code from all the not essential things, so you will see the problems better. Bye, bearophile
Dec 17 2011
Heromyth <bitworld qq.com> == Quote from bearophile (bearophileHUGS lycos.com)'s articleHeromyth:describe how to use opCmp. Probably you need to accept a const Object, and to use override. I suggest to strip your code from all the not essential things, so you will see the problems better.I have defined a opCmp function to overload comparison operators, then how can I use it correctly?I don't have an answer yet, but I suggest you to look at the D docs thatBye, bearophileI tested public override int opCmp(Object o) and got the same result. The D document suggests rewriting a < b into a.opCmp(b) < 0 comparing operation between two class object. Maybe the compiler should give some messages for not using "a < b". Is it a compiler bug? Can anyone give some suggertion. It will be well grateful.
Dec 17 2011
Heromyth wrote:
I can use it like this:
int b = t1.opCmp(info);
and is it right like this:
int b = t1 < info;
In my test code, I get different value for b. What can I do?
Nothing because the call of the operator `<' interprets the result of the
call of `opCmp', which is constant in this case!
Remember that the result of `opCmp' is used for at least the operators `<',
`>', `<=' and `>='.
-manfred
Dec 17 2011
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;
Dec 17 2011
== Quote from Jesse Phillips (jessekphillips+d gmail.com)'s articleOn Sat, 17 Dec 2011 14:06:48 +0000, Heromyth wrote: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 */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;
Dec 17 2011