[eeps] : : Proposal for /\ and \/ operators

Raimo Niskanen <>
Fri Feb 27 11:47:32 CET 2009


On Thu, Feb 26, 2009 at 11:28:06AM +0100, Pierpaolo Bernardi wrote:
> On Thu, Feb 26, 2009 at 11:12 AM, Raimo Niskanen <
>  <raimo%>> wrote:
> 
> > On Thu, Feb 26, 2009 at 10:55:34AM +0100, Pierpaolo Bernardi wrote:
> > > On Thu, Feb 26, 2009 at 10:35 AM, Raimo Niskanen <
> > >  <raimo%> <
> > raimo% <raimo%>>> wrote:
> > >
> > >
> > > > Can you explain to a non-mathematician (me) why you have defined
> > > > (E1 /\ E2) as min(E1, E2) and
> > > > (E1 \/ E2) as max(E1, E2). To me it seems counterintuitive
> > > > since /\ looks like a mountain hence max
> > > > and \/ looks like a valley hence min.
> > > > And I do not want to fully understand Lattice theory
> > > > to understand which operator is which. I am a simple programmer.
> > >
> > >
> > > It's not ROK's invention it's common mathematical usage (derived from
> > > Boolean algebra, I think).
> > >
> > > The symbol  \/ derives from the letter V, abbreviation of "vel" (= or in
> > > latin).
> > >
> > > I'm not sure where /\ comes from (maybe an inverted V?)
> >
> > Yes I am quite familiar with /\ being AND and \/ being OR.
> > That is in the basic math courses at University.
> 
> 
> I meant, it's common to use these symbols for min and max,
> like they are used in boolean algebra.
> 
> In an algebra on the values true and false, where true and false are
> ordered,
> with false < true, the operation OR is the same as MAX and AND is the same
> as MIN.
> 
> (Think false = 0, true = 1, and all will snap in place :)

Thank you for sorting this out for me.
I still do not find it obvious why it is false < true,
could as well be the other way around, or...
Luckily, in Erlang, because f < t in ASCII, false < true;
atoms are sorted in lexical order.

> 
> P.

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-- 

/ Raimo Niskanen, Erlang/OTP, Ericsson AB



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