On Sep 22, 2019, at 02:08, Nutchanon Ninyawee <m...@nutchanon.org> wrote:
>
> Link is a language feature that allows multiple variable names to always
> refer to the same underlying object define in a namespace.
> For now, if the variable a link with b. I will denote as a >< b or link('a',
> 'b')
>
> a = 2
> a >< alpha # link 'a' with 'alpha'
> b = 3
> print(b**alpha) # print 9
> alpha = 3
> print(b**a) # print 27
How would this work? I can think of a few options, but they all either badly
slow down every variable use, don’t work with locals, or require >< to be
handled at compile time. Do you have at least a sketch of how this works?
Also, do you have a real-life use case? Usually when you want the equivalent of
“variable references” in Python, you just stick the value in a list or an
explicit namespace; why isn’t that sufficient here? Also, usually you’re doing
it to share a reference with a function, not just using another name in the
same namespace; why do you need actual references here but not in the more
general and more often-desired case?
And finally, a whole bunch of questions on behavior:
What happens if you `del a`?
Is there a syntax to unlink variables? It seems like you’d want that at least
at the interactive REPL.
Is there any way to discover whether two names are linked?
If you link `a >< b` and then link `b >< c`, does that make a three-way link,
or unlink a from b?
If you link two locals and capture them both in a closure, are the closures a
single cell, or two cells that reference captured names that happen to be
linked?
What if you link two names in a class body?
What if it’s inside code passed to eval or exec with normal locals and globals?
Or with a custom dict subclass or Mapping class for one or the other?
Can you link arbitrary targets (e.g., self.a >< self.b, or even a >< b[10]), or
just bare names?
If you call globals(), do you get back some kind of dict-like object that knows
about the links (and can be inspected), or something that looks like a
plain-old dict but if you assign to its `a` you also change `b`, or something
that looks like a plain-old dict but if you assign to its `a` you unlink it?
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