Re: PIZZA time again :-)

From: vc <boston103_at_hotmail.com>
Date: 2 Sep 2005 13:05:06 -0700
Message-ID: <1125691506.385188.218910@f14g2000cwb.googlegroups.com>

mAsterdam wrote:
> dawn wrote:
> >mAsterdam wrote:
> >>>>Assume
> >>>>1. there is a meaningful (or at least consequential)
> >>>>difference between:
> >>>>
> >>>> toppings([salami, mozarella, onions]).
> >>>> and
> >>>> toppings([mozarella, onions, salami]).
> [snip]
> >>Consider
> >>
> >> merge(ListOfLists, MergedList).
> >>
> >>Now
> >>
> >>merge ([[salami, mozarella, onions][mozarella, onions, salami]], M).
> >>
> >>should fail because salami is before mozarella in the first list,
> >>and after it in the second. It can't preserve the order.
> >
> > I don't know how you define a merge when there isn't
> > an ordering defined on the type.
> > Is there such a function? Your lists are ordered here,
> > but your domain/type is not, unless you choose something
> > like alpha order.

> That is another way of asking the same question.
> What should 'merge' do when the order is not
> in the values (as it would be if we took the
> ordering defined on the type) but just in
> their position, relative to other values.
> It is what I'm trying to find out.

Since 'merge' is commonly defined for lists with the same ordering, the function cannot be applied to lists with different orderings, e.g [a, b] and [b,a,c] (ordering is defined by an element position in the list) clearly cannot be merged. Received on Fri Sep 02 2005 - 15:05:06 CDT