[Python-3000] Sky pie: a "var" keyword

[Nick Coghlan]

Neil Toronto wrote:
> As long as patches are flying willy-nilly and we're just kicking around 
> ideas like puppies, I thought I'd offer one of my own.
> 
> No, not a puppy. An idea. Of course, if it ends up beaten to death, I 
> might rather it were a puppy. My apologies if it's been discussed in 
> some other form.
> 
> It occurs to me that some of Python's gotchas are due to the compiler 
> not being able to determine whether the user intends to *create* a 
> variable, or *modify* one.

Any proposal such as this also needs to addresses all of the *other* name 
binding statements in Python:

   try/except
   for loop
   with statement
   def statement
   class statement

All of these statements bind a name in the current scope regardless of whether 
or not that name is used elsewhere in the current scope or an outer scope.

The current behaviour of assignment statements is identical - they all bind a 
name in the current scope (with augmented assignment statement expecting that 
the name already be defined).

This proposal introduces a *new* statement (var) to take on the meaning of the 
current assignment statement, and proposes to give assignment statements a 
special "rebind" behaviour that will silently break code like the following 
due to the missing 'var' on the inner x variable:

for x in range(10):
   def some_op(y):
       x = y+2
       real_op(x, y)
   for y in range(x):
       some_op(x, y)

I prefer my non-local effects to be explicit, thank-you-very-much. A solid -1 
here.

Regards,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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