[Python-Dev] Switch statement

M.-A. Lemburg mal at egenix.com
Fri Jun 16 10:29:51 CEST 2006

Greg Ewing wrote:
> M.-A. Lemburg wrote:
>> My personal favorite is making the compiler
>> smarter to detect the mentioned if-elif-else scheme
>> and generate code which uses a lookup table for
>> implementing fast branching.
> But then the values need to be actual compile-time
> constants, precluding the use of symbolic names,
> values precomputed a run time, etc.

Good point.

> A new statement would allow us to simply document
> that the case values are *assumed* constant, and
> then the implementation could cache them in a dict
> or whatever.

That would a very well hidden assignment of a "constantness"
property to a symbol or expression. We'd also run into
the problem of not knowing when to evaluate those
case expressions, e.g. at function compile time,
at run-time when first entering the switch statement,

Marc-Andre Lemburg

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