On Wed, Oct 24, 2012 at 2:05 PM, Patrick Walton <[email protected]> wrote:
> On 10/24/12 12:50 PM, Niko Matsakis wrote:
>>
>> Patrick—
>>
>> I think what you're saying -1 on here is some kind of purity inference?
>> That doesn't seem to be what was proposed, though.
>>
>> In fact, I *believe* Nathan's point was merely that it's useful
>> sometimes to document "purity" in order to express the intention of the
>> API, and that in those cases it's nice to write it explicitly, just as
>> it's nice to have the types of parameters and return types written
>> explicitly.  This does not seem to be in disagreement with what you said
>> about reserving the right to become impure.
>
>
> Oh, in that case I totally agree. I thought Nathan was asking for the purity
> specified in the function signature to always match the inferred purity of
> the function--in particular, for the compiler to enforce that a pure
> function is never marked impure. That was what I was objecting to. If I
> misinterpreted I apologize.
>

Patrick interpreted my suggestion correctly, but on second thought I
withdraw it.  Requiring inferred-pure functions to be explicitly
marked pure is inconvenient, just as if a type may be inferred as
~[u8] but the API designer may want to declare it ~[mut u8] for future
flexibility.

>
> Patrick
>


Nathan

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