[Python-Dev] Simple Switch statementZ

[Ka-Ping Yee]

On Sun, 25 Jun 2006, Guido van Rossum wrote:
> What do you think of Nick C's 'once'?

It's a bit closer to the right meaning... but what about:

    def f(x):
        def g(y):
            return y + once x
        return g

Does "once" mean not really once here, but "once for each new function
object that's created for g"?

> Right. But there are all sorts of objects that are compared by object
> identity (e.g. classes, modules, even functions) which may contain
> mutable components but are nevertheless "constant" for the purpose of
> switch or optimization. Let's not confuse this concept of constness
> with immutability.

That's a good point.  We need a concept like "stable for equality"
separate from "constant", since "constant" and "immutable" will mislead
those who are used to the meanings of these words in other languages.


-- ?!ng