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Topic: PROLOG does SO have NOT() !!
Replies: 3   Last Post: Nov 20, 2012 3:33 PM

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Graham Cooper

Posts: 4,495
Registered: 5/20/10
Re: PROLOG does SO have NOT() !!
Posted: Nov 20, 2012 3:33 PM
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On Nov 20, 11:52 pm, Frederick Williams
<> wrote:
> Graham Cooper wrote:

> > Exactly the same way we use not().
> > Failure to return a result can be programmed for ANY PREDICATE
> > [...]
> > You can PROGRAM the predicate NOT(...)
> > for any predicate with a FINITE SET OF ARGUMENT VALUES!
> Is this "negation as failure"?

It's Negation as OTHER.

You can hand program Negation in prolog code for any predicate with a
finite domain.

refundable(CUST) :- taxtype( CUST, personal )
refundable(CUST) :- taxtype( CUST, business )
refundable(CUST) :- taxtype( CUST, company )
not(refundable(CUST)) :- taxtype(CUST, other)

if( refundable(C) , processreturn(C) ).

This works for BOOLEAN ARG predicates like if, or, and, iff, xor,
nand, nor, ..

nand(X) :- not(X).

even if you nest them.

?- or( if(1,0) , if(1,X) )
X = 1


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