On Thursday 06 February 2003 11:49 am, Guido van Rossum wrote:
> > If this is just for fun, why stop with just "trinary"?
>
> (Which BTW is a non-word; the correct term is "ternary".)
>
> > How about one of the following (depending on ease of parsing)?
> > These look even more like list comprehension.
> >
> > x = (e1 if c1 e2 if c2 e3 if c3 ... else d)
>
> Doesn't parse. The concatenation of two expressions is not
> always distinguishable from a single expression: consider c1 = f and
> c2 = (1, 2).
>
> > x = (e1 if c1 else e2 if c2 else e3 if c3 ... else d)
>
> That works.
Now that I've had a little more time to thing about it, this
suggestion of a n-ary form is nothing more than nested ternary forms
with extra parentheses removed:
(a1 if c1 else (a2 if c2 else b2))
could be allowed to be written as
(a1 if c1 else a2 if c2 else b2)
and, if you want:
(a1 if c1 else
a2 if c2 else
b2)
Other sub-threads of this thread are discussing how to parse these
ternary operators if the parentheses are not required. I think the
parentheses *should* be required (see below for why) and so it would
be nice to allow this extended form and not require the inner set of
parentheses when doing "tail nesting" (to invent a term).
BEWARE: UNPYTHONIC UGLINESS FOLLOWS!
On the other hand, if the parentheses are NOT required, we get a whole
host of *UGLY*, absolutely unreadable, nesting possibilities:
a if b else c if d else e <==> (a if b else c) if d else e
and even worse
a if b if c else d else e <==> a if (b if c else d) else e
And what about statements
if a if b else c if d else e:
f
elif g if h if i else j else k:
l
else:
m
Of course, any feature can be abused, but this seems *too* abusable.
Gary Herron
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