On Tue, 19 May 2009 21:41:08 -0700, Aaron Brady wrote:
> On May 19, 11:20 pm, Paul Rubin <http://phr...@nospam.invalid> wrote:
>> Steven D'Aprano <ste...@remove.this.cybersource.com.au> writes:
>> > (4) the caller is responsible for making sure he never shares data
>> > while looping over it.
>>
>> > I don't think I've missed any possibilities. You have to pick one of
>> > those four.
>>
>> I wonder if the compiler can check that a given function doesn't change
>> any data. Then:
>>
>> @pure
>> def f(x):
>> return x*sqrt(x) + 3 # does not mutate any data
>>
>> @pure
>> def g(x): ... # likewise
>>
>> s = parallel_dot_product(parallel_map(f, vec), parallel_map(g,vec))
>
> You can do the basics of this using the 'ast' module. Just check that
> no nodes in the ast tree are Assign nodes, including augmented assign.
> Then 'f' is defined as:
>
> f= pure( '''
> return x*sqrt(x) + 3 # does not mutate any data
> ''' )
>
> Untested.
Can you explain how you can tell that there are no side-effects from
x*sqrt(x)+3 ? What if I have this?
class Funny(object):
def __add__(self, other):
global parrot
parrot += 1
return 5 + other
x = Funny()
--
Steven
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