Re: [boost] Classpath to C++ conversion

From: Tushar (tushar_at_[hidden])
Date: 2005-03-28 09:06:15

On Fri, 2005-03-25 at 01:06, Andreas Pokorny wrote:
First, Thanks all who replied.  
> On Thu, Mar 24, 2005 at 01:14:57PM +0530, Tushar <tushar_at_[hidden]> wrote:
> > Hi all,
> > 
> > I am thinking of converting GNU Classpath used for GCJ to C++. I have
> > following reasons about why to do this.
> 
> The Classpath in C++ would be the runtime linker path, and a mapping of
> namespaces onto directories? How would one implement such a concept, and
> for what use?
To have same uniform API as JAVA. 
> 
> Or is the classpath the whole library api?
> 
> > 1. C++ requires a Good OOPs library with well defined api. Java has that
> > . While C++ also have many of them, most do not look truly  object 
> > oriented.
> Could you elaborate "Good OOPs"? 
> Do you think that only object oriented librarys are good enough? 
Well,no. One can have good library without OOPS, but when one want to
use a language that supports OOPS and one wants to design using OOPS in
that language, then I think it is must.

> 
> > 2.C++ has much of the libs using STL. The only problem is STL is not a
> > object oriented.
> Where is the problem? Containers are object, algorithms are not. Looks
> perfectly good to me. 
Yes it is. But that is case of pure algorithms like sorting. But for
many case, one wants to combine data and algorithm.(If I am correct,
this is called encapsulation in OOPS).  So for example, I can have a
linked list which can sort itself. According to STL, I will create a
linked list and pass it to method sort. 
> > (See STL Tutorial and reference) This really makes it
> > difficult to think in OO and implement in STL. Particularly in STL,
> > T a,b
> > T a=b means a is separate entity and same for b. This make problem in
> > many case where one wants just pointer e.g File handling and
> > manipulation of large buffer.
> Where is the relation between value/pointer/reference semantic, and oop? 
> Btw, you need to understand language semantics before implementing
> anything in that language. 
> 
What I mean to say is that in java, I have

void foo()
{
        String str="0123456789";
        List l;
        l=new List();
        for(i=0;i<10;++i)
                l.insert(str);

        
}
What will happen in STL is that we will get array to 10 chars copied to
list at every insert. So at last, there should be 10 copies of same
string. In java, just a pointer to actual string is stored. 

> 
>  
> > My idea is that API specification is already defined for java. And it
> > seems much complete.I mean to say more complete then if start deciding
> > from scratch -:). Why not to use java then?
> I doubt that reusing the design makes much sense, because it was designed 
> for a different language, a language without templates, without references,
> multiple inheritance, without operators and without destructors. Thus there 
> are lots of things that can be handled nicer. 
As java is a subset of C++, the same design can be used. Lets go one by
one.
1.Templates - Templates can be used for primitive types. I do not know
how to use it for other things like sorting of objects. Why should we
have a piece of code that sorts just object of class X.(I am talking
about run time code, not just source code). Instead we can write a
procedure which will sort all objects using a pointer to some abstract
class that will be extended by all objects that need to be sorted. When
using templates, other problem is that to forget to overload operators
like '=' and many a times this gives lots of problem. For sorting with
template I need to implement all '<','>','=,'==','=<','>='. I find it
better to implement compareTo() only. 

2.All java objects use reference for accessing real objects. So I do not
think this can be problem. 
> > Difference bet proposed C++ and Java
> > 1.Everything is a pointer other them simple atomic data types.(Same)
> References are helpful, try to implement a swap without references. Why
> should you prune C++ here?
We can. But if a have a method that need to allocate memory and return
it back to caller, then how to handle this with reference. E.g

void readConfig(String **str1,String **str2)
{
        //try to get str1 from config file
        //try to get str2 from config file
        //if failed, throw some exception
        //allocate str1 and copy string from config file
        //allocate str2 and copy from config file	
        //if failed to allocate then throw some exception
}	
 
> 
> > 4.Every thing is subclass of Object(Same).
> Why should one pay for a deep hierarchy that is never used? You should
> ask yourself why java needs to have that common base class.
Yes. Seems I need to do more R & D over object. One need I can see now
is that it can act as common pointer that all can access with some
common method. Like, when writing LinkedList, we can write it to work
with object and use casting for real use. I was also thinking to
implement synchronization using object using wait,notify etc.
Regards,
Tushar

>  
> 
> 
> Regards
> Andreas Pokorny
> 
> 
> ______________________________________________________________________
> 
> _______________________________________________
> Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost