What ever happened to ENGINES? 
Author Message
 What ever happened to ENGINES?

Hello,

Some years ago I used a Scheme system that supported something called
"engines".   If I recall, the construct worked something like this:

  (ENGINE 100 (lambda () <arbitrary computation>))

The above call would run the <arbitrary computation> for 100 time units.
Either the computation would finish and ENGINE would return the value,
or the computation would NOT finish and ENGINE would return a continuation
(a closure), which could be passed again to ENGINE for further evaluation.
With ENGINEs, one could implement concurrency and fair search.  But the
scheme FAQ doesn't mention them, and as far as I know, current Scheme
implementation don't support them.  Is this so?   If so, why?  They seem
so useful!




Sun, 20 Sep 1998 03:00:00 GMT  
 What ever happened to ENGINES?

Quote:

> Some years ago I used a Scheme system that supported
> something called "engines".  [...]

Chez Scheme supports them.  They're implemented in terms of a
timer interrupt mechanism.  I haven't used engines, but I've
used the timer.  It's very handy.

-thant



Sun, 20 Sep 1998 03:00:00 GMT  
 What ever happened to ENGINES?
Hi!

DS>Some years ago I used a Scheme system that supported something called
DS>"engines".   If I recall, the construct worked something like this:

It's still only in the PC Scheme (the original and the Geneva at least - I
suppos it's in the Ibuki, too). No other Scheme seems to have implemented
something like it. It's really too bad - engines are quite useful and a really
powerful abstraction. But the problem is, as I think, that they are hard to
implement portable. And most Scheme systems seem to go only the portable way.

bye, Georg



Sat, 26 Sep 1998 03:00:00 GMT  
 
 [ 3 post ] 

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