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-rw-r--r--Demo/metaclasses/Eiffel.py70
1 files changed, 35 insertions, 35 deletions
diff --git a/Demo/metaclasses/Eiffel.py b/Demo/metaclasses/Eiffel.py
index 38ee6bc..d9c8a9a 100644
--- a/Demo/metaclasses/Eiffel.py
+++ b/Demo/metaclasses/Eiffel.py
@@ -4,19 +4,19 @@ For example,
class C:
def m1(self, arg):
- require arg > 0
- return whatever
+ require arg > 0
+ return whatever
ensure Result > arg
can be written (clumsily, I agree) as:
class C(Eiffel):
def m1(self, arg):
- return whatever
+ return whatever
def m1_pre(self, arg):
- assert arg > 0
+ assert arg > 0
def m1_post(self, Result, arg):
- assert 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
@@ -28,10 +28,10 @@ post-condition with that defined in the derived class', for example:
class D(C):
def m1(self, arg):
- return whatever**2
+ return whatever**2
def m1_post(self, Result, arg):
- C.m1_post(self, Result, arg)
- assert Result < 100
+ 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.
@@ -42,13 +42,13 @@ 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
+ pass
but one could equally write a derived class that makes a stronger
requirement:
def m1_pre(self, arg):
- require arg > 50
+ 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).
@@ -66,27 +66,27 @@ 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
+ 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:
- apply(self.pre, args, kw)
- Result = apply(self.func, (self.inst,) + args, kw)
- if self.post:
- apply(self.post, (Result,) + args, kw)
- return Result
+ if self.pre:
+ apply(self.pre, args, kw)
+ Result = apply(self.func, (self.inst,) + args, kw)
+ if self.post:
+ apply(self.post, (Result,) + args, kw)
+ return Result
class EiffelHelper(MetaHelper):
__methodwrapper__ = EiffelMethodWrapper
@@ -99,12 +99,12 @@ 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
+ 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)