Re: Most basic nothrow, pure, @safe functions?

[Steven Schveighoffer]

On Thu, 20 Mar 2014 22:14:59 -0400, Steven Schveighoffer  
<schvei...@yahoo.com> wrote:

On Thu, 20 Mar 2014 22:00:15 -0400, Walter Bright  
<newshou...@digitalmars.com> wrote:

On 3/20/2014 6:40 PM, Steven Schveighoffer wrote:
How do they affect global state?

Mutexes implicitly share state. It's the reason they exist. They can't  
be pure, because pure functions don't share state.

I view it differently. I feel like locking and unlocking a mutex is  
pure. After calling lock, the same thing *always* happens. After  
unlocking, the same thing *always* happens. It's a weird thing -- when  
you lock a mutex, you own it after it's locked. It's no longer shared.  
It can be thought of as pulling memory out of the heap to temporarily  
own, and then putting it back, just like memory allocation (which is  
considered pure).

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.

-Steve