Re: Process Placement in Occam 2.1

[Michael Goldsmith <michael@xxxxxxxx>]

Kai,

On 11/03/2006 14:24, Koehne Kai wrote:
> I have a specific question concerning the Occam 2.1 standard. The question is if this is legal occam: 
>  
> SEQ
>   PROCESSOR 1              -- PROCESSOR outside PLACED PAR!!
>     SKIP
>   SKIP

My belief is that it is not; it doesn't really make sense.  The compiler 
would have to invent a baton-passing event (which you could yourself, of 
course, to achieve the effect), and that is contrary to the WYSIWIG 
philosophy of occam.  The configuration language for deploying occam 
programs was a bit of a bolt-on; PLACED PAR is the only component that 
intrudes into the language proper.

> The BNF grammar that is part of the standard allows it:
>  
> parallel     = ...
>                 | placedpar
>  
> placedpar = PLACED PAR
>                     { placedbar }
>                 | PLACED PAR replicator
>                     placedpar
>                 | PROCESSOR expression
>                     process
>  
> process    = ...
>                 | parallel
>                 | ...

That just looks like laziness in drawing up the grammar, avoiding repeating 
the constructor forms in both "outer" and "nested" context.  I don't have a 
copy to hand; does it treat the productions for IF and ALT differently?

Best,
--
M