🚀 go-pugleaf

CSP is a fine theoretical entity, but it surely is not a programming language,
since CSP (as defined in Hoare's book) "programs" are not capable of actually 
doing anything.  (Hoare's definition of parallel composition is inadequate.)

Occam is the rather ugly result of one attempt at including the elegant
concepts of CSP in a practical and efficient programming language.
(Note that, ignoring the procedural/functional differences, the main 
conceptual difference between CSP and occam involves the action of parallel 
composition.)

As far as the debate over the 'copying controversy' goes, let me offer my
own opinions.  Whether one prefers a shared-variable paradigm or a message-
passing paradigm, anyone should recognize that it is just plain ugly to
mix the use of these paradigms.  In the absence of a virtual shared-memory
(in which the underlying message-passing is made invisible to the programmer),
physically distributed memory forces us to accept a message-passing paradigm.

At a purely practical level, the 'copy-penalty' is probably not a real issue
since any program that aspires to efficieny (when compared to sequential
programs) must be coarse-grained enough so as to make the communication
time negligible when compared to the computation time.  When this is the case
the 'copy-penalty' will obviously be negligible also.

Incidentally, the ALT statement in occam is NOT a source of inefficiency for
occam programs.  Since occam channels may be accessed by only two processes,
the system designers were able to implement the ALT statement quite
efficiently.  An ALT process enables all of its inputs, and then deschedules
itself until there is a matching output process for one of the ALT guards.  
Only then does the ALT process get rescheduled.  Since the ALT process does not
consume processor cycles during the waiting period (other processes can be 
executed), ALT execution is quite efficient.


Jonathan