List comprehensions

[Jesse Sweeney]

On Wed, 22 Dec 1999 10:51:39 GMT, thantos at chancel.org (Alexander Williams)
wrote:

>On 22 Dec 1999 10:28:52 GMT, Albert Hofkamp <hat at se-46.wpa.wtb.tue.nl>
>wrote:

[ snip ]

>> Another matter is scoping. I hope that code like
>> i := 30
>> ys := [ 4 ]
>> xs := [ i ] + [ i+15, for i in ys ] + [ i+1 ]
>>
>>is well-defined.
>>I'd like to have xs == [ 30, 19, 31 ] at the end, but I am too new to
>>Python to say anything useful about scoping.
>>Is this what you'd expect, and is it feasible ?
>
>Certainly; I don't expect scoping in the LCs will be much of an
>issue.  The above mock-up should be completely defined under present
>scoping rules.

Well, I haven't actually installed the patch in question, but as I understand it
the comprehension-using code above would translate to the following current
Python:

    i = 30
    ys = [4]
    xs = [i]
    for i in ys:
        xs = xs + [i+15]
    xs = xs + [i+1]

which leaves xs as [30, 19, 5], not [30, 19, 31] as Albert was suggesting.
Someone who's actually used the patch might correct me, but I'd be surprised if
the scoping rules were different to the rules for for loops.

	Cheers, Jesse.