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digitalmars.D - Remove Object.toString()?

reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
I'm pretty sure most of the "debug" functions in the internal classes such 
as Object will be removed at 1.0, but just to make sure, will 
Object.toString() be removed?  The same information is available through 
Object.classinfo.name, and it's really irritating to have to type 
"std.string.toString" every time I want to use toString() in a class member 
function.
Feb 19 2005
parent reply Ben Hinkle <Ben_member pathlink.com> writes:
In article <cv902c$1jit$1 digitaldaemon.com>, Jarrett Billingsley says...

I'm pretty sure most of the "debug" functions in the internal classes such 
as Object will be removed at 1.0, but just to make sure, will 
Object.toString() be removed?  The same information is available through 
Object.classinfo.name, and it's really irritating to have to type 
"std.string.toString" every time I want to use toString() in a class member 
function. 


you can use just .toString to get the toString at module scope instead of the
class toString:







Also Object.clasinfo.name cannot be overridden like toString can be, so the two
have pretty different behaviors.

-Ben
Feb 19 2005
parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
 you can use just .toString to get the toString at module scope instead of 
 the
 class toString:


Forgot about the global scope operator.  Thanks!


 Also Object.clasinfo.name cannot be overridden like toString can be, so 
 the two
 have pretty different behaviors.


Well what's the point in having Object.toString() in the first place?  It 
can be overridden, so what?  It's supposed to return the classinfo.name, and 
nothing else.  So what's the purpose?
Feb 20 2005
next sibling parent reply Ben Hinkle <Ben_member pathlink.com> writes:
 Also Object.clasinfo.name cannot be overridden like toString can be, so 
 the two have pretty different behaviors.


Well what's the point in having Object.toString() in the first place?  It 
can be overridden, so what?  It's supposed to return the classinfo.name, and 
nothing else.  So what's the purpose? 


Why do you say it is supposed to always return classinfo.name? 

and in those languages toString returns a human-readable summary of the object.
Personally I'd like D's Object.toString to include a unique id as well as the
class name so that you can tell one object apart from another. Without that I
still have to rely on code like
printf("obj is %x\n",obj);
instead of
writefln("obj is ", obj);
Feb 20 2005
next sibling parent reply =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
Ben Hinkle wrote:


 Personally I'd like D's Object.toString to include a unique id as well as the
 class name so that you can tell one object apart from another. Without that I
 still have to rely on code like
 printf("obj is %x\n",obj);
 instead of
 writefln("obj is ", obj);


I second that, it would be nice if it worked like in Java for instance:


 The toString method for class Object returns a string consisting of the
 name of the class of which the object is an instance, the at-sign
 character ` ', and the unsigned hexadecimal representation of the hash
 code of the object.


Sample D implementation:


     char[] toString()
     {
 	return std.string.format("%d %x", this.classinfo.name, this.toHash());
     }


Optionally it could use the pointer/reference, instead of the hashcode ?

--anders
Feb 20 2005
parent =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
 Sample D implementation:
 

     char[] toString()
     {
     return std.string.format("%d %x", this.classinfo.name, this.toHash());
     }




I meant to write "%s %x", but for some reason the above worked ?

--anders
Feb 20 2005
prev sibling parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
 My guess is that toString in D is supposed to be like toString in Java and 

 and in those languages toString returns a human-readable summary of the 
 object.


I suppose that'd be fine, but wouldn't it make more sense to put that kind 
of stuff in the typeinfo?


 Personally I'd like D's Object.toString to include a unique id as well as 
 the
 class name so that you can tell one object apart from another.


Might be a bit tricky.  If by "unique ID" (I have never used Java so I have 
no idea what its ID numbers are) you mean some kind of ID number that is 
assigned incrementally to each newly allocated object (so the first one has 
an ID of 1, the next has 2, and so on), I'm not real sure how easy that'd be 
to implement it as part of the language.  Or how practical.  If by ID you 
mean a hash.. well, that'd be nice if the toHash() method did more than 
return an int representation of the pointer ;)
Feb 21 2005
next sibling parent =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
Jarrett Billingsley wrote:


 Might be a bit tricky.  If by "unique ID" (I have never used Java so I have 
 no idea what its ID numbers are) you mean some kind of ID number that is 
 assigned incrementally to each newly allocated object (so the first one has 
 an ID of 1, the next has 2, and so on), I'm not real sure how easy that'd be 
 to implement it as part of the language.  Or how practical.  If by ID you 
 mean a hash.. well, that'd be nice if the toHash() method did more than 
 return an int representation of the pointer ;) 


Java uses the hash code, and they tend to look somewhat similar:

o.java:

 public class o
 {
   public static void main(String[] args)
   {
     Object o = new Object();
     System.out.println(o);
   }
 }


java.lang.Object 47b480

o.d:

 import std.stdio;
 
 char[] toString(Object o)
 {
   return std.string.format("%s %x", o.classinfo.name, o.toHash());
 }
 
 void main()
 {
   Object o = new Object();
   writefln("%s", toString(o));
 }


Object 406fe0


And the default toHash will not just return the pointer forever:

internal/object.d:

 // BUG: this prevents a compacting GC from working, needs to be fixed


So just because the *current* implementation of toString() or toHash()
returns something, doesn't mean it's identical to that implementation ?

--anders

PS. You should take a quick peek at Java, if you haven't already.
     D is something of a cross-over language between C and Java...
Feb 21 2005
prev sibling parent Ben Hinkle <Ben_member pathlink.com> writes:
In article <cvcmkd$2nc5$1 digitaldaemon.com>, Jarrett Billingsley says...

 My guess is that toString in D is supposed to be like toString in Java and 

 and in those languages toString returns a human-readable summary of the 
 object.


I suppose that'd be fine, but wouldn't it make more sense to put that kind 
of stuff in the typeinfo?


The summary should contain information about the instance, too. For example
"[FooClass 1234abcd x:33 y:66 flag:false]". In order to create the string you
have to run a function. It could be possible to put a slot in the classinfo and
have users call that whenever they need the string but using a vtable slot is
pretty much the same functionality and is the standard way to allow class
objects to customize behavior. 


 Personally I'd like D's Object.toString to include a unique id as well as 
 the
 class name so that you can tell one object apart from another.


Might be a bit tricky.  If by "unique ID" (I have never used Java so I have 
no idea what its ID numbers are) you mean some kind of ID number that is 
assigned incrementally to each newly allocated object (so the first one has 
an ID of 1, the next has 2, and so on), I'm not real sure how easy that'd be 
to implement it as part of the language.  Or how practical.  If by ID you 
mean a hash.. well, that'd be nice if the toHash() method did more than 
return an int representation of the pointer ;) 


I had forgotten exactly what the id is that Java prints. Looking at the Java doc
the string contains the hash code as hex. I guess that sacrifices guaranteed
uniqueness but makes it easy to write toString. Since the hash code is probably
the pointer in Java as well as D it is pretty much the same as printing out the
address. I don't know what Java implementations with copying collectors do.
Feb 21 2005
prev sibling parent John Demme <me teqdruid.com> writes:
Jarrett Billingsley wrote:

 Well what's the point in having Object.toString() in the first place?  It 
 can be overridden, so what?  It's supposed to return the classinfo.name, and 


I've never seen that.  In fact, I frequently use it for other things.


 nothing else.  So what's the purpose? 


I believe when one does something like:
Object o = ....
writefln("%s", o);

format is supposed to call the toString method and use that.

John
Feb 20 2005