1 files changed, 0 insertions, 113 deletions
diff --git a/Demo/metaclasses/Eiffel.py b/Demo/metaclasses/Eiffel.py
deleted file mode 100644
index 8c39746..0000000
--- a/Demo/metaclasses/Eiffel.py
+++ /dev/null
@@ -1,113 +0,0 @@
-"""Support Eiffel-style preconditions and postconditions.
-
-For example,
-
-class C:
-    def m1(self, arg):
-        require arg > 0
-        return whatever
-        ensure Result > arg
-
-can be written (clumsily, I agree) as:
-
-class C(Eiffel):
-    def m1(self, arg):
-        return whatever
-    def m1_pre(self, arg):
-        assert arg > 0
-    def m1_post(self, Result, arg):
-        assert Result > arg
-
-Pre- and post-conditions for a method, being implemented as methods
-themselves, are inherited independently from the method.  This gives
-much of the same effect of Eiffel, where pre- and post-conditions are
-inherited when a method is overridden by a derived class.  However,
-when a derived class in Python needs to extend a pre- or
-post-condition, it must manually merge the base class' pre- or
-post-condition with that defined in the derived class', for example:
-
-class D(C):
-    def m1(self, arg):
-        return arg**2
-    def m1_post(self, Result, arg):
-        C.m1_post(self, Result, arg)
-        assert Result < 100
-
-This gives derived classes more freedom but also more responsibility
-than in Eiffel, where the compiler automatically takes care of this.
-
-In Eiffel, pre-conditions combine using contravariance, meaning a
-derived class can only make a pre-condition weaker; in Python, this is
-up to the derived class.  For example, a derived class that takes away
-the requirement that arg > 0 could write:
-
-    def m1_pre(self, arg):
-        pass
-
-but one could equally write a derived class that makes a stronger
-requirement:
-
-    def m1_pre(self, arg):
-        require arg > 50
-
-It would be easy to modify the classes shown here so that pre- and
-post-conditions can be disabled (separately, on a per-class basis).
-
-A different design would have the pre- or post-condition testing
-functions return true for success and false for failure.  This would
-make it possible to implement automatic combination of inherited
-and new pre-/post-conditions.  All this is left as an exercise to the
-reader.
-
-"""
-
-from Meta import MetaClass, MetaHelper, MetaMethodWrapper
-
-class EiffelMethodWrapper(MetaMethodWrapper):
-
-    def __init__(self, func, inst):
-        MetaMethodWrapper.__init__(self, func, inst)
-        # Note that the following causes recursive wrappers around
-        # the pre-/post-condition testing methods.  These are harmless
-        # but inefficient; to avoid them, the lookup must be done
-        # using the class.
-        try:
-            self.pre = getattr(inst, self.__name__ + "_pre")
-        except AttributeError:
-            self.pre = None
-        try:
-            self.post = getattr(inst, self.__name__ + "_post")
-        except AttributeError:
-            self.post = None
-
-    def __call__(self, *args, **kw):
-        if self.pre:
-            self.pre(*args, **kw)
-        Result = self.func(self.inst, *args, **kw)
-        if self.post:
-            self.post(Result, *args, **kw)
-        return Result
-
-class EiffelHelper(MetaHelper):
-    __methodwrapper__ = EiffelMethodWrapper
-
-class EiffelMetaClass(MetaClass):
-    __helper__ = EiffelHelper
-
-Eiffel = EiffelMetaClass('Eiffel', (), {})
-
-
-def _test():
-    class C(Eiffel):
-        def m1(self, arg):
-            return arg+1
-        def m1_pre(self, arg):
-            assert arg > 0, "precondition for m1 failed"
-        def m1_post(self, Result, arg):
-            assert Result > arg
-    x = C()
-    x.m1(12)
-##    x.m1(-1)
-
-if __name__ == '__main__':
-    _test()