On Mon, 23 Apr 2007 11:11:04 +0200, Paul Giaccone <paulg@cinesite.co.uk> wrote:
Marco wrote:
Well, the last word is up to the author's library, however I'd be surprised if the following relations were not valid:
associativity: or_< T1, or_<T2, T3> > == or_< T1, T2, T3 > == or_< or_<T1, T2,>, T3 > and_< T1, and_<T2, T3> > == and_< T1, T2, T3 > == and_< and_<T1, T2,>, T3 >
Excuse my mathematical pedantry and going off topic. The operations or_ and and_ are binary, not ternary. Each of the middle expressions is, by definition (that is, mathematical consensus), equal to at least one of the corresponding outer terms. One or both of the equalities in each of the above relations is therefore tautologous (that is, always true).
The only requirement for associativity is:
or_< T1, or_<T2, T3> > == or_< or_<T1, T2,>, T3 > #1 and_< T1, and_<T2, T3> > == and_< and_<T1, T2,>, T3 > #2
I agree the only requirements for associativity are the equalities #1 and #2. The middle term in my relations has to be seen as the demonstration (IMO) that associativity really holds. Marco -- Using Opera's revolutionary e-mail client: http://www.opera.com/mail/