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From: siva@csgrad.cs.vt.edu (Siva Challa)
Newsgroups: comp.lang.beta
Subject: Re: Method overloading in BETA
Date: 7 Nov 1997 21:25:10 GMT
Organization: Virginia Tech Computer Science
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In article <3461A0F9.3752@marvin.informatik.uni-dortmund.de>,
Holger Tuerk  <htuerk00@marvin.informatik.uni-dortmund.de> wrote:
>Hello,
>
>Siva Challa wrote:
>> I am new to the BETA language. I have a general question. Is 'method
>> overloading' allowed in BETA?
>
>If 'method overloading' means that different methods with the same name
>are invoked depending on the number and types of the arguments you
>passed, the answer is no.
>You have to choose different designations for your patterns.
>
>Holger



Thank you very much for your answer to my question on 'method
overloading' in BETA.

I have a follow up question on the same issue. Let me tell you a little
bit about what I am trying to do before asking the question. 

I am trying to see  if 'method overloading' can be faked with existing
features of a language, if it does not support the 'method overloading'
feature. 

For example,  Modula-3 does not support method
overloading. But, it has run time type checking. It has a common base class
for all classes called 'REFANY'. You  can typecast any class to this
class and typecast it back. Modula-3  also supports default values for method
arguments. 

Let me take an example ( I am using a pseudo code representation}
     
     let A, B, and C be classes.

     class A {
        methodF (b : B, c: C); 
	methodF (c : C);
     }

In languages like C++, I can invoke methodF with one argument or two
arguments. The compiler can figure out which method to invoke depending
on the arguments.

If I want to have similar facility in Modula-3, I can use the following
(again i am using a pseudo code syntax for simplicity)

     Class A {
        methodF_B_C(b : B, c: C);
        methodF_C(c : C);
        methodF(r : REFANY, c : REFANY := NIL)
     }

     Here methodF has a default value for the parameter c. So, we can
call methodF with one argument or two arguments. In the one argument
call, it assumes that the second argument value is NIL.

     In the implementation of methodF, I can check the type of the
first argument,  and then invoke the right method (methodF_B_C or methodF_C) 
by typecasting the arguments to their respective types. The
implementation of methodF can look like the following pseudo code:

     methodF(r : REFANY, c : REFANY := NIL) {
	if (typeOf(r) is B) then
          call methodF_B_C((typecast r to B), (typecast c to C));
        else if (typeOf(r) is C) then
          call methodF_C((typecast r to C));
     }

I hope I am able to explain it. Now, my question is, IS THERE ANY WAY IN
THE BETA LANGUAGE TO FAKE 'METHOD OVERLOADING'. In Modula-3, I needed
default values for arguments, runtime typechecking, and a common base class 
called REFANY. I don't know much about the language BETA.  I am not
able to figure out if I can do it in BETA too.


Please let me know if my example is clarifying my question. I would
appreciate any help with the answer.

Thanks again.
Siva
siva@vt.edu