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Replies: 49   Last Post: Jan 13, 2012 2:37 PM

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 kirby urner Posts: 3,690 Registered: 11/29/05
Posted: Dec 12, 2011 11:57 AM

On Sun, Dec 11, 2011 at 10:10 PM, Dan Christensen <dc@dcproof.com> wrote:
> Using another kind of computer-like language, DC Proof, we can represent a function f mapping set A to set B as follows:
>
> ALL(x):[x in A => f(x) in B]  (replace "in" by epsilon)
>

B = [ f(x) for x in A ]

would work for me but I'd still to flesh out f and set A for this to
work. set type supports intersection, union and so on.

One question is how much to stress the set concept, big in the 1960s
thanks to New Math and still a feature in Saxon, Singapore etc.
(inheritors of much Dolciani -type thinking, subclasses we might say).

Why not just treat sets as one more type and stop trying to consider
which type is "most primitive"? I'm from the Wittgensteinian camp on
matters mathematical, which nets me some ridicule from Hansen, but I
say it saves me time.

I'm not as tempted to waste so many hours on the union and
intersection of sets when we could also be playing with lists, tuples
etc. Lists of lists, or multi-dimensional lists, are worth relatively
more time, sets relatively less.

Along the DM track, we're free to make these base-level pioneering
adjustments because we're not hampered by the AM (analog math)
detritus, the cultural baggage, the flotsam and jetsam. A new kind
of freedom, helps build ubuntu (community spirit).

DC Proof looks interesting. I used to play WFF 'n Proof a lot, used
that RPN style if that's what it was, not unlike LISP which they'll
hasten to tell you is different etc. Fun world.

Kirby

> In words: For all x, if x is an element of A, then f(x) is an element B.
>
> This simple notation completely characterizes all functions of 1 variable.
>
> In the tutorial included with my program is a worked example (#6) illustrating the composition of functions, e.g. f(g(x)), along with suitable exercises with hints and full solutions.
>
> Dan

Date Subject Author
12/11/11 kirby urner
12/12/11 Dan Christensen
12/12/11 kirby urner
12/12/11 Dan Christensen
12/13/11 kirby urner
12/13/11 Dan Christensen
12/13/11 kirby urner
12/13/11 Dan Christensen
12/13/11 kirby urner
12/13/11 Joe Niederberger
12/13/11 Dan Christensen
12/13/11 kirby urner
12/13/11 Dan Christensen
12/15/11 Joe Niederberger
12/15/11 kirby urner
12/15/11 Joe Niederberger
12/15/11 kirby urner
12/15/11 Joe Niederberger
12/15/11 kirby urner
12/15/11 Joe Niederberger
12/15/11 kirby urner
12/15/11 Joe Niederberger
12/15/11 kirby urner
12/16/11 Joe Niederberger
12/16/11 kirby urner
12/16/11 Dan Christensen
12/16/11 Joe Niederberger
12/17/11 Joe Niederberger
12/17/11 kirby urner
12/17/11 Dan Christensen
12/18/11 Wayne Bishop
12/18/11 Joe Niederberger
12/18/11 kirby urner
12/23/11 Dan Christensen
12/23/11 Wayne Bishop
12/24/11 Louis Talman
12/23/11 Joe Niederberger
12/23/11 kirby urner
12/23/11 Wayne Bishop
12/24/11 Joe Niederberger
12/24/11 Wayne Bishop
12/24/11 Joe Niederberger
12/24/11 kirby urner
12/24/11 Joe Niederberger
12/24/11 Wayne Bishop
12/24/11 Dan Christensen
12/25/11 Dan Christensen
12/25/11 Dan Christensen
1/13/12 Joe Niederberger
1/13/12 kirby urner