Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!gatech!udel!haven!adm!cmcl2!kramden.acf.nyu.edu!brnstnd
From: brnstnd@kramden.acf.nyu.edu (Dan Bernstein)
Newsgroups: comp.lang.misc
Subject: Re: After aliassing -- parallelisation?
Message-ID: <7244:Nov1009:14:5490@kramden.acf.nyu.edu>
Date: 10 Nov 90 09:14:54 GMT
References: <24674:Nov906:50:1890@kramden.acf.nyu.edu> <5499@lanl.gov>
Organization: IR
Lines: 30

In article <5499@lanl.gov> jlg@lanl.gov (Jim Giles) writes:
> From article <24674:Nov906:50:1890@kramden.acf.nyu.edu>, by brnstnd@kramden.acf.nyu.edu (Dan Bernstein):
> > One thing that helps detect this situation is pure functions, which
> > depend only on their arguments and local variables initialized from
> > their arguments.  [...]
> Finally an agreement!  Pretty much the same thing I said.

Shall we get into an argument about who posted first? :-) (I did!)

> However,
> I'm not too sure about your default - shouldn't 'pure' be the
> default and 'impure' require the extra declaration? :-)

I'm pretty sure that impure is the right default, for various reasons.

> > [...]            (Clearly subroutines of pure functions must be pure.)
> And how do you determine _this_ at compile time? :-)  Again, only
> half kidding.  This is another thing that the loader would be very
> good at enforcing.  I can _imagine_ arcane schemes involving header
> files to do this earlier than load-time, but it again requires that
> the headers and the routines themselves actually match.

Jim, can you please shed your paranoia about .h files that don't reflect
c files?

There's absolutely nothing arcane about putting purity into prototypes
in header files, and enforcing these restrictions locally. It works
perfectly.

---Dan