[Python-ideas] Introducing where clauses

Georg Brandl g.brandl at gmx.net
Tue Jun 23 09:11:07 CEST 2009

Carl Johnson schrieb:
> Andrey Popp wrote:
>> I am not about list comprehension only, there are other cases for
>> where-clause, for example lambdas:
>>    f = lambda x: (x, y) if x > 0 else (x, 0) where y = g(x)
> Yuck. This reminds me of why I gave up on the Haskell tutorial I was
> working through. The reading of this line keeps bouncing back and
> forth. "OK, function f, passing in x, returning x, y… Wait? What's y?
> Is that from an external scope? Anyway, here's an if-else clause, and
> oh, there's the y! It's the same as g(x). OK, so where all did they
> use y? Hmm, lets see, looks like just the one spot…" 

I know what you mean :)  I think "where" is best used where you all
but know exactly what the where-bound name refers to, but have to spell
it out for the stupid computer somewhere...


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