Re: Hat-Observe N+M Counter?

Malcolm Wallace <[email protected]> Fri, 17 Nov 2006 14:00:20 +0000
Newsgroups gmane.comp.lang.haskell.hat
Organization Dept of Computer Science, University of York
Message-ID <[email protected]>
"Maik Barz" <[email protected]> wrote:

> I am wondering if there's no more M+N Counter. In the documentation is
> an explanation that it shows the number of evaluated and nonevaluated
> functions when using :info. Is there an option to set this option?

You are right, the (m+n) count of (reduced applications + unevaluated apps)
has been removed.  I could not find anything in the commit log messages
to say why.  Would this be a useful feature to re-instate?

There are actually three counts available:
  * reduced applications
  * applications entered but never completed (blackholes)
  * applications that were never demanded
The original (m+n) count included the first two of these.  We reasoned
that the third count was uninteresting, because if a value was never
demanded, then it had absolutely no effect on the computation.

Regards,
    Malcolm