Suggestion for Condition variables

[Sean Kelly]

Graham St Jack wrote:
> Here is a suggestion for an extension to D to handle pthread-like 
> condition variables in a way that fits neatly with the "synchronized" 
> keyword.
> 
> I use threads a lot, and quite often find that I need conditions, but 
> even though all the functionality is there in the locks library, it is 
> galling that I can't use the same mutex as the "synchronized" keyword.
> 
> The alternatives seem to be to:
> * Eliminate or ignore the synchronized keyword and use a library all the 
>   time.
> * Make the language "aware" of the library, and provide a way of getting 
> an object's mutex.
> * Add some more keywords to handle conditions directly.

I've been thinking about this as well, and I think it helps that the 
monitor location is already specified in the ABI.  This should allow 
library use of monitors whether there's any official language support or 
not.

> My suggestion is for the last, because I like synchronized, and because 
> I don't like making the language aware of the libraries.
> 
> 
> So, the suggestion is to add:
> 
> * A "condition" keyword that behaves for the most part just like a bool 
> data type, but is actually a condition variable.

Personally, I'd be happy with library code for this, so long as it could 
use the built-in monitors.  I'd also like a bit more flexibility with 
how locks are obtained and such, but perhaps this is better left for later.


Sean