[REBOL] Re: Commercial-quality REBOL programmers needed
From: joel:neely:fedex at: 17-Aug-2002 8:25
Hi, Dick,
One other thought on this...
[reffy--ulrich--net] wrote:
> Hi List,
>
> I am bored ...
>
> Does the evaluation of the expression: a + b
>
> Happen synchronously, or asynchronously
>
> Are the values of 'a' and 'b' currently exclusive to the process
> that can perform the '+' operation or are they in 'shared' mode ?
>
As pointed out previously, REBOL is single-threaded. However (as
usual with REBOL), there's more to the story. The values/behaviors
of the words A and B above may be "entangled" in other ways that we
can't observe just from that fragment of code. For example:
hidden_counter_1: hidden_counter_2: 0
a: func [] [
hidden_counter_1: hidden_counter_1 +
hidden_counter_2: hidden_counter_2 + 1
]
b: func [] [
hidden_counter_1: hidden_counter_1 + hidden_counter_2
hidden_counter_2: hidden_counter_2 + 1
hidden_counter_1
]
In this case, the value of A + B would differ from the value of
B + A due to their mutual involvement with hidden state.
I realize that this isn't specifically about traditional concurrency,
but long ago I stopped interpreting "concurrent" as "happening at the
same time" and began interpreting it as "may happen (or be interleaved)
in an arbitrary order" which makes it a much more interesting concept
IMHO.
-jn-
--
; Joel Neely joeldotneelyatfedexdotcom
REBOL [] do [ do func [s] [ foreach [a b] s [prin b] ] sort/skip
do function [s] [t] [ t: "" foreach [a b] s [repend t [b a]] t ] {
| e s m!zauafBpcvekexEohthjJakwLrngohOqrlryRnsctdtiub} 2 ]
