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From: mbk@caffeine.engr.utk.edu (Matt Kennel)
Subject: Re: Eiffel and Java
Date: 1996/11/01
Message-ID: <55ditr$pnh@gaia.ns.utk.edu>#1/1
X-Deja-AN: 193749991
references: <55562c$nkd@mulga.cs.mu.OZ.AU>
 <1996Oct31.162218.8386@schbbs.mot.com>
followup-to: 
 comp.lang.eiffel,comp.lang.ada,comp.lang.sather,comp.lang.java.advocacy,comp.object
organization: University of Tennessee,
 Knoxville and Oak Ridge National Laboratory
reply-to: %%spam repellent: remove this prefix%%kennel@msr.epm.ornl.gov
newsgroups: 
 comp.lang.eiffel,comp.lang.ada,comp.lang.sather,comp.lang.java.advocacy,comp.object
Date: 1996-11-01T00:00:00+00:00
List-Id: <comp.lang.ada>


David L. Shang (shang@corp.mot.com) wrote:
: In article <55562c$nkd@mulga.cs.mu.OZ.AU> fjh@mundook.cs.mu.OZ.AU (Fergus  
: Henderson) writes:
: > Suppose I have two existing library classes (perhaps supplied by different
: > vendors) which have some commonality, but don't inherit from a common
: > base class.  In Sather, one can simply create a new interface and
: > declare these classes to be instances of this interface, without
: > modifying the existing code.
: > 
: > (Is that possible in Java?)
: > 

: No. Java supports only top-down class hierarchy construction
: (from superclass to subclasses), but not bottom-up: from
: subclasses to superclass.

: But Sather's superclass construction is limited to non-parametrerized
: classes only.

This isn't true, at least in 1.1.  The following compiles and executes. 

-------------------------------------------------------
-- demonstrate abstract superclass over a parameterized type. 
-------------------------------------------------------
abstract class $OVER{T} > $P{T} is
   feature1(arg:T);
end;

abstract class $P{T} is
  feature1(arg:T);
  feature2(arg:T);
end; 

class CONCRETE{T} < $OVER{T} is
   feature1(arg:T) is #OUT + "In feature\n"; end;
   create:SAME is return new; end; 
end;    

   
class MAIN is
	main is
	  #OUT + "Hello World.\n";
	  
	  ob :$OVER{INT} := #CONCRETE{INT}; 
	  ob.feature1(42);

        end;
end;

--------------------------------
: Transframe provides a more powerful superclass construction that 
: can support parameterized classes.

: Suppose we have two existing classes
: ....

I believe that Sather could express the same concept. 

: David Shang
: 	

--
Matthew B. Kennel/mbk@caffeine.engr.utk.edu/I do not speak for ORNL, DOE or UT
Oak Ridge National Laboratory/University of Tennessee, Knoxville, TN USA/ 
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