an oop question

[Julieta Shem]

ram at zedat.fu-berlin.de (Stefan Ram) writes:

> Julieta Shem <jshem at yaxenu.org> writes:
>>clarify.  If I wish for an empty stack, I wish I could just say
>>>>> Stack()
>>Stack()
>>and if I wish for a nonempty stack, I'd write
>>>>> Stack(1, Stack(2, Stack(3, Stack())))
>>Stack(1, Stack(2, Stack(3, Stack())))
>
>   If this is all,
>
>   main.py
>
> class Stack:
>     def __init__( self, *args ):
>         self.data = [ args[ 0 ], args[ 1 ]]if len( args ) else []
>     def __str__( self ):
>         if len( self.data ):
>             return f"Stack({self.data[0]}, {self.data[1]})"
>         else:
>             return f"Stack()"
>
> print( Stack() )
>
> print( Stack(1, Stack(2, Stack(3, Stack()))) )
>
>   output
>
> Stack()
> Stack(1, Stack(2, Stack(3, Stack())))

Thanks!  But we've left behind a more basic requirement --- the Stack
class wishes for all the methods already written in some class called
Pair, which has a certain connection with a class Empty.  This
requirement has been implicit in the first message in this thread,
though.  I didn't make it explicit.  (In other words, this part of the
thread only makes sense by taking into account all the previous messages
up in the thread.)