Re: [Python-Dev] Switch statement

Mon, 19 Jun 2006 09:27:34 -0700

Guido van Rossum wrote: 
On 6/18/06, Josiah Carlson <[EMAIL PROTECTED]> wrote:
  
[...] Offering arbitrary expressions whose
meaning can vary at runtime would kill any potential speedup (the
ultimate purpose for having a switch statement), [...]
    

Um, is this dogma? Wouldn't a switch statement also be a welcome
addition to the readability? I haven't had the time to follow this
thread (still catching up on my Google 50%) but I'm not sure I agree
with the idea that a switch should only exist for speedup.

A switch-statement offers only a modest readability improvement over if-elif chains.  If a proposal introduces a switch-statement but doesn't support fast dispatch, then it loses much of its appeal.  Historically, the switch-statement discussions centered around fast dispatch without function call overhead or loss of direct read/write to local variables (see sre_compile.py and sre_parse.py for code would would see a speed benefit but almost no improvement in readability).


Raymond





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