[Python-Dev] Simple Switch statementZ

Mon Jun 26 02:43:27 CEST 2006

On 2006年6月25日, 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