IIRC NaN is readonly, but you'd need to be able to guarantee the lexical scope
between your function definition and the global object did have any shadowing :D
--Oliver
On Nov 28, 2012, at 1:32 PM, Axel Rauschmayer <a...@rauschma.de> wrote:
> Would returning NaN be impure (apart from running the risk of it having been
> changed to something different, globally)?
>
> On Nov 28, 2012, at 21:35 , Oliver Hunt <oli...@apple.com> wrote:
>
>>
>> On Nov 28, 2012, at 12:25 PM, Waldemar Horwat <walde...@google.com> wrote:
>>
>>> On Wed, Nov 28, 2012 at 5:39 AM, Marius Gundersen <gunder...@gmail.com>
>>> wrote:
>>> On Wed, Nov 28, 2012 at 1:20 PM, Andreas Rossberg <rossb...@google.com>
>>> wrote:
>>> Second, due to the extremely impure nature of JavaScript, there aren't
>>> many useful pure functions you could even write. For example, your
>>> 'sum' function is not pure, because the implicit conversions required
>>> by + can cause arbitrary side effects.
>>>
>>> Functions passed to the array methods map, reduce, filter, etc would be
>>> good candidates for pure/side-effect-free functions. These functions
>>> shouldn't alter any state; they should only return a new value based on the
>>> parameter they were sent.
>>>
>>> You haven't addressed Andreas's point: Almost any function you write is
>>> nonpure, including your sum example. As a fun exercise, go ahead and write
>>> a pure version of your sum example.
>>>
>>> Waldemar
>> Here you go:
>>
>> function sum(a, b) {
>> var undefined;
>> switch (typeof a) {
>> case "number":
>> case "string":
>> break;
>> default:
>> return +undefined;
>> }
>> switch (typeof b) {
>> case "number":
>> case "string":
>> break;
>> default:
>> return +undefined;
>> }
>> return a + b;
>> }
>>
>>
>>
>>>
>>> _______________________________________________
>>> es-discuss mailing list
>>> es-discuss@mozilla.org
>>> https://mail.mozilla.org/listinfo/es-discuss
>>
>> _______________________________________________
>> es-discuss mailing list
>> es-discuss@mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>
> --
> Dr. Axel Rauschmayer
> a...@rauschma.de
>
> home: rauschma.de
> twitter: twitter.com/rauschma
> blog: 2ality.com
>
_______________________________________________
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
