[Python-Dev] Simple Switch statement

[Ka-Ping Yee]

On Sat, 24 Jun 2006, Raymond Hettinger wrote:
> The main points of contention are 1) a non-ambiguous syntax for assigning
> multiple cases to a single block of code, 2) how to compile variables as
> constants in a case statement, and 3) handling overlapping cases.
>
> Here's a simple approach that will provide most of the benefit without
> trying to overdo it:
[...]
> The result of f(x) should be hashable or an exception is raised.
> Cases values must be ints, strings, or tuples of ints or strings.
> No expressions are allowed in cases.

I like this proposal.  It eliminates all of the surprises that have
been hiding in the other switch proposals so far, except for throwing
an exception when the switch expression isn't hashable.  But i can
easily live with that restriction, since the cases are all literals
that must be hashable, so if the switch expression comes out to some
other type then it probably really is an error that should be caught.

I agree with the general feeling that it would be nice to have a bit
more flexibility, but so far i haven't thought of any way to get more
flexibility without more surprises, so until a better idea comes along
i'm happy with this one.


-- ?!ng