[openbeos] Re: POSIX thread safety, was: Re: Waiting and waiting

  • From: Scott Mansfield <thephantom@xxxxxxx>
  • To: openbeos@xxxxxxxxxxxxx
  • Date: Wed, 11 Dec 2002 07:43:43 -0800

On Wednesday 11 December 2002 07:31, you wrote:
> > On Tuesday 10 December 2002 11:51, you wrote:
> > > The definition I read didn't say that a reentrant function has to
> > > return
> > > the same thing each time it's called with the same parameters.
> >
> > That would be "idempotent," not re-entrant.
>
> A function f: X -> X is called idempotent, if f * f = f. The above
> definition matches something like stateless deterministic, I would say.

Same for f: D -> D, it is idempotent if f(f x) = f x for all x in D?  Sorry, 
it's been a while and my calculus is a bit hazy.  :-)

I was referring to the jargon commonly used to describe an idempotent function 
as that which performs some action exactly once (initialization, for 
example), even if called multiple times.

Hasta,
Scott

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