On Friday, 21 March 2014 at 03:04:36 UTC, Steven Schveighoffer
wrote:
Thinking about it some more, I see what you mean -- an unshared
mutex is useless.
But at the same time, some "logically" pure functions cannot be
so without mutexes. E.g. memory allocation.
Since when does "shared" => "impure" ?
If the function takes a pointer to shared data, then you are
explicitly saying "this function depends on this shared data".
But as long is it isn't referencing some *other* global directly,
it is perfectly pure.
For example:
//----
int i = 5;
void foo(int* p) pure
{++p;}
void main() pure
{
foo(&p);
}
//----
This is "textbook" of a pure function changing global state.
----------------
So the way I see it: shared => pinter to mutex => touching it is
fair game => can be legit pure (IMO).
