ÿØÿà JFIF    ÿÛ „ ( %!1!%*+...983,7(-.- usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyc000064400000011030152351201610015133 0ustar00ó ¿œ^c@s™dZddlmZmZmZdefd„ƒYZdefd„ƒYZdefd„ƒYZed d iƒZd „Z e d kr•e ƒnd S(sÐSupport 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. iÿÿÿÿ(t MetaClasst MetaHelpertMetaMethodWrappertEiffelMethodWrappercBseZd„Zd„ZRS(cCs‹tj|||ƒyt||jdƒ|_Wntk rLd|_nXyt||jdƒ|_Wntk r†d|_nXdS(Nt_pret_post(Rt__init__tgetattrt__name__tpretAttributeErrortNonetpost(tselftfunctinst((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyRDs   cOsh|jrt|j||ƒnt|j|jf||ƒ}|jrdt|j|f||ƒn|S(N(R tapplyRRR (R targstkwtResult((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt__call__Ss   (Rt __module__RR(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyRBs t EiffelHelpercBseZeZRS((RRRt__methodwrapper__(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyR[stEiffelMetaClasscBseZeZRS((RRRt __helper__(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyR^stEiffelcCs0dtfd„ƒY}|ƒ}|jdƒdS(NtCcBs#eZd„Zd„Zd„ZRS(cSs|dS(Ni((R targ((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1fscSs|dkstdƒ‚dS(Nisprecondition for m1 failed(tAssertionError(R R((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1_prehscSs||kst‚dS(N(R(R RR((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1_postjs(RRRRR (((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyRes  i (RR(Rtx((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt_testds t__main__N(( t__doc__tMetaRRRRRRRR"R(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt>s lib64/python2.7/Demo/metaclasses/Eiffel.pyc000064400000011030152360672710014337 0ustar00ó ¿œ^c@s™dZddlmZmZmZdefd„ƒYZdefd„ƒYZdefd„ƒYZed d iƒZd „Z e d kr•e ƒnd S(sÐSupport 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. iÿÿÿÿ(t MetaClasst MetaHelpertMetaMethodWrappertEiffelMethodWrappercBseZd„Zd„ZRS(cCs‹tj|||ƒyt||jdƒ|_Wntk rLd|_nXyt||jdƒ|_Wntk r†d|_nXdS(Nt_pret_post(Rt__init__tgetattrt__name__tpretAttributeErrortNonetpost(tselftfunctinst((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyRDs   cOsh|jrt|j||ƒnt|j|jf||ƒ}|jrdt|j|f||ƒn|S(N(R tapplyRRR (R targstkwtResult((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt__call__Ss   (Rt __module__RR(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyRBs t EiffelHelpercBseZeZRS((RRRt__methodwrapper__(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyR[stEiffelMetaClasscBseZeZRS((RRRt __helper__(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyR^stEiffelcCs0dtfd„ƒY}|ƒ}|jdƒdS(NtCcBs#eZd„Zd„Zd„ZRS(cSs|dS(Ni((R targ((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1fscSs|dkstdƒ‚dS(Nisprecondition for m1 failed(tAssertionError(R R((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1_prehscSs||kst‚dS(N(R(R RR((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1_postjs(RRRRR (((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyRes  i (RR(Rtx((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt_testds t__main__N(( t__doc__tMetaRRRRRRRR"R(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt>s lib64/python2.7/Demo/newmetaclasses/Eiffel.pyc000064400000014162152361426620015060 0ustar00ó ¿œ^c@s±dZddlmZdefd„ƒYZdefd„ƒYZddd„ƒYZd efd „ƒYZ d efd „ƒYZ d „Z e dkr­e eƒe e ƒndS(s6Support Eiffel-style preconditions and postconditions.iÿÿÿÿ(t FunctionTypetEiffelBaseMetaClasscBs eZd„Zed„ƒZRS(cCs,|j|ƒtt|ƒj||||ƒS(N(tconvert_methodstsuperRt__new__(tmetatnametbasestdict((s2/usr/lib64/python2.7/Demo/newmetaclasses/Eiffel.pyRs cCsßg}xo|jƒD]a\}}|jdƒs=|jdƒrUt|tƒstt‚qt|tƒr|j|ƒqqWx`|D]X}|jd|ƒ}|jd|ƒ}|s·|r|j||||ƒ||s  4