toHash => pure, nothrow, const, @safe

[deadalnix]

Le 13/03/2012 17:06, Andrei Alexandrescu a écrit :
> On 3/13/12 10:47 AM, deadalnix wrote:
>> This problem is pretty close to garbage collection. Let's use pure as
>> example, but it work with other qualifier too.
>>
>> function are marked pure, impure, or pure given all function called are
>> pure (possibly pure). Then you go throw all possibly pure function and
>> if it call an impure function, they mark it impure. When you don't mark
>> any function as impure on a loop, you can mark all remaining possibly
>> pure functions as pure.
>
> Certain analyses can be done using the so-called worklist approach. The
> analysis can be pessimistic (initially marking all functions as not
> carrying the property analyzed and gradually proving some do carry it)
> or optimistic (the other way around). The algorithm ends when the
> worklist is empty. This approach is well-studied and probably ought more
> coverage in compiler books. I learned about it in a graduate compiler
> class.
>
> However, the discussion was about availability of the body. A
> worklist-based approach would need all functions that call one another
> regardless of module. That makes the analysis interprocedural, i.e.
> difficult on large codebases.
>
>
> Andrei

I expect the function we are talking about here not to call almost all 
the codebase. It would be scary.