scope of function parameters (take two)

Chris Angelico rosuav at gmail.com
Mon May 30 23:34:43 EDT 2011


On Tue, May 31, 2011 at 1:18 PM, Daniel Kluev <dan.kluev at gmail.com> wrote:
> On Tue, May 31, 2011 at 2:05 PM, Chris Angelico <rosuav at gmail.com> wrote:
>> Infinitely-nested scoping is simply one of the casualties of a
>> non-declarative language.
>
> Well, this is not accurate, as you can have 'infinitely-nested
> scoping' in python, in form of nested functions. For example, you can
> use map(lambda x: <expressions with x, including other
> map/filter/reduce/lambda's>, list_of_x), and you will have your
> isolated scopes. Although due to lambdas supporting only expressions,
> following this style leads to awkward and complicated code (and/or
> instead if, map instead for, and so on).

That's an incredibly messy workaround, and would get ridiculous if you
tried going many levels in. It's like saying that a C-style 'switch'
statement can be implemented in Python using a dictionary of
lambdas... and then trying to implement fall-through. But you're
right; a lambda does technically create something of a nested scope -
albeit one in which the only internal variables are its parameters.

Chris Angelico



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