On Mon, 31 Oct 2022 at 09:05, Julieta Shem <[email protected]> wrote:
>
> Julieta Shem <[email protected]> writes:
>
> [...]
>
> >> . If you should, however, be talking about the new "type hints":
> >> These are static and have "Union", for example, "Union[int, str]"
> >> or "int | str".
> >
> > I ended up locating such features of the language in the documentation,
> > but I actually am not interested in declaring the type to the compiler
> > (or to the reader).
> >
> > I was looking for a solution like yours --- thank you! ---, although I
> > was hoping for handling that situation in the construction of the Stack
> > object, which was probably why I did not find a way out. Right now I'm
> > looking into __new__() to see if it can somehow produce one type or
> > another type of object depending on how the user has invoked the class
> > object.
> >
> > Terminology. By ``invoking the class object'' I mean expressions such
> > as Class1() or Class2(). ``Class1'' represents the object that
> > represents the class 1. Since the syntax is that of procedure
> > invokation, I say ``invoking the class object''.
>
> An experiment. What's my definition of Stack? It's either Empty or
> Pair, so it's a union. So let us create two inner classes (that is,
> inner to Stack) and make them behave just like Empty and Pair. Using
> __new__(), we can produce a Stack object that is sometimes Empty() and
> sometimes Pair(...).
>
The most straight-forward way to represent this concept in an
object-oriented way is subclassing.
class Stack:
... # put whatever code is common here
class Empty(Stack):
... # put Empty-specific code here, possibly overriding Stack methods
class Pair(Stack):
... # ditto, overriding or augmenting as needed
This way, everything is an instance of Stack, but they are still
distinct types for when you need to distinguish.
ChrisA
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