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For review: PEP 308 - If-then-else expression

holger krekel pyth at devel.trillke.net
Sun Feb 9 14:05:23 EST 2003 
Aahz wrote:
> In article <r8ahfto4.fsf at morpheus.demon.co.uk>,
> Paul Moore  <gustav at morpheus.demon.co.uk> wrote:
> >
> >As a follow-on question - does anyone seriously feel that a
> >significant portion of c.l.p is likely to have its opinion swayed by
> >arguments made in this thread?
> 
> Not by arguments, no, but by ideas.  I believe that the swing voters are
> those who are mildly sympathetic to conditional expressions, but who
> find one or all of the various proposals abhorrent.  If someone can come
> up with a truly Pythonic idiom for conditional expressions, I believe
> it'll pass.

that's my guess, too. 

> I suspect that my criteria are similar to many other people's:
> 
> * must have clear left-to-right or right-to-left meaning
> 
> * must look vaguely readable even when abused as the conditional for if
> statements

Maybe Roman Suzi (IIRC) has found one (short-circuiting)

    cond -> (true_expr, false_expr)

which i am currently thinking about.  

my current pros:

    - reads from left to right

    - not too easy to abuse, reads rather nicely

    - *may* be extended to support dispatching of more than two expr

my current cons:

    - the order (true, false) or (false, true) is not obvious
      especially if you are converting  [false, true](bool(cond))

    - the parser might not be taught this grammar (?)

hmmm.

    holger
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