Aminet 30/Aminet 30 (1999)(Schatztruhe)[!][Apr 1999].iso/Aminet/dev/lang/SmallEiffel.lha/SmallEiffel/lib_std/comparable.e

Text File | 1998-12-22 | 3KB | 118 lines

-- This file is  free  software, which  comes  along  with  SmallEiffel. This
-- software  is  distributed  in the hope that it will be useful, but WITHOUT
-- ANY  WARRANTY;  without  even  the  implied warranty of MERCHANTABILITY or
-- FITNESS  FOR A PARTICULAR PURPOSE. You can modify it as you want, provided
-- this header is kept unaltered, and a notification of the changes is added.
-- You  are  allowed  to  redistribute  it and sell it, alone or as a part of
-- another product.
--          Copyright (C) 1994-98 LORIA - UHP - CRIN - INRIA - FRANCE
--            Dominique COLNET and Suzanne COLLIN - [e-mail]
--                       http://www.loria.fr/SmallEiffel
--
deferred class COMPARABLE
   --
   -- All class handling COMPARABLE object with a total order relation
   -- should inherit from this class.
   --

feature

   infix "<" (other: like Current): BOOLEAN is
     -- Is `Current' strictly less than `other'?
      require
     other_exists: other /= Void
      deferred
      ensure
     asymmetric: Result implies not (other < Current);
      end;

   infix "<=" (other: like Current): BOOLEAN is
     -- Is `Current' less or equal `other'?
      require
     other_exists: other /= Void
      do
     Result := not (Current > other)
      ensure
     definition: Result = (Current < other) or is_equal(other);
      end;

   infix ">" (other: like Current): BOOLEAN is
     -- Is `Current' strictly greater than `other'?
      require
     other_exists: other /= Void
      do
     Result := (other < Current)
      ensure
     definition: Result = (other < Current)
      end;

   infix ">=" (other: like Current): BOOLEAN is
     -- Is `Current' greater or equal than `other'?
      require
     other_exists: other /= Void
      do
     Result := not (Current < other)
      ensure
     definition: Result = (other <= Current)
      end;

   in_range(lower, upper: like Current): BOOLEAN is
         -- Return true if `Current' is in range [`lower'..`upper']
      do
     Result := (Current >= lower) and then (Current <= upper)
      ensure
     Result = (Current >= lower and Current <= upper)
      end;

   compare(other: like Current): INTEGER is
     -- Compare `Current' with `other'.
     -- `<'  <==> `Result < 0'
     -- `>'  <==> `Result > 0'
     -- Otherwise `Result = 0'.
      require
     other /= Void
      do
     if Current < other then
        Result := -1
     elseif other < Current then
        Result := 1
     end
      ensure
     (Result < 0) = (Current < other);
     (Result = 0) = not (Current < other or Current > other);
     (Result > 0) = (Current > other)
      end;

   min(other: like Current): like Current is
     -- Minimum of `Current' and `other'.
      require
     other /= Void
      do
     if Current < other then
        Result := Current
     else
        Result := other
     end;
      ensure
     Result <= Current and then Result <= other;
     compare(Result) = 0 or else other.compare(Result) = 0
      end;

   max(other: like Current): like Current is
     -- Maximum of `Current' and `other'.
      require
     other /= Void
      do
     if other < Current then
        Result := Current;
     else
        Result := other;
     end;
      ensure
     Result >= Current and then Result >= other;
     compare(Result) = 0 or else other.compare(Result) = 0
      end;

end -- COMPARABLE