Re: Eiffel and Java

[mbk@caffeine.engr.utk.edu (Matt Kennel)]

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/ 
  I would not, could not SAVE ON PHONE,    |==================================
  I would not, could not BUY YOUR LOAN,    |The US Government does not like
  I would not, could not MAKE MONEY FAST,  |spam either.  It is ILLEGAL!
  I would not, could not SEND NO CA$H,     |USC Title 47, section 227
  I would not, could not SEE YOUR SITE,    |p (b)(1)(C) www.law.cornell.edu/
  I would not, could not EAT VEG-I-MITE,   | /uscode/47/227.html
  I do *not* *like* GREEN CARDS AND SPAM!  |==================================
               M A D - I - A M!