Operation   : Linux premium131.web-hosting.com 4.18.0-553.44.1.lve.el8.x86_64 #1 SMP Thu Mar 13 14:29:12 UTC 2025 x86_64
Software     : Apache
Server IP    : 162.0.232.56 | Your IP: 216.73.216.111
Domains      : 1034 Domain(s)
Permission   : [ 0755 ]

�
��^c@s�dZd
dl
mZmZmZ
def
d��YZdef
d��YZdef
d��YZed	d
i�Zd
�Z	e
dkr�e	�
ndS(s�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.

i����(t	MetaClasst
MetaHelpertMetaMethodWrappertEiffelMethodWrapperc
BseZ
d�Zd
�ZRS(cCs�tj
||
|�
yt||jd
�|_Wntk
rL


d|_n
Xyt||jd�|_Wntk
r�


d|_n
XdS(Nt_pret_post(Rt__init__tgetattrt__name__tpretAttributeErrortNonetpost(tselftfunctinst((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyRDs










c
Osh|jrt
|j|
|�
nt
|j|jf
|
|�}|jrdt
|j|f
|
|�
n|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EiffelHelperc
BseZ
eZRS((RRRt__methodwrapper__(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyR[s
tEiffelMetaClassc
BseZ
eZRS((RRRt
__helper__(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyR^s
tEiffelcCs0d
tf
d��Y}|�}
|
j
d�

dS(Nt
Cc
Bs#eZ
d�Zd
�Zd�ZRS(cSs|
d
S(Ni
((R
targ((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1fs
cSs|
d
kstd�
�
dS(Nisprecondition for m1 failed(
tAssertionError(R
R((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pytm1_prehs
cSs|
|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(Rt
x((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt_testds
	
t__main__N((t__doc__tMetaRR
RRRRRR"R(((s//usr/lib64/python2.7/Demo/metaclasses/Eiffel.pyt<module>>s