🚀 go-pugleaf

In article <1992Aug12.210954.15241@cs.ucla.edu>, mika@oahu.cs.ucla.edu (Mikhail Karpoukhin) writes:
> Does anybody know the prolog for UNIX which supports
> the fuzzy unification of floating point numbers,     
> that is two floating point numbers are considered 
> equal if | X - Y | =< FUZZVALUE  and this FUZZVALUE
> can be changed by user? I know that VM/Prolog has
> this feature, but it works on mainframe.

I suspect that IBM Prolog's method is more sophisticated that this,
although the manual implies that an absolute test is done.

Quintus Prolog's library has the "fuzzy" module, which defines (I quote):

    For a fixed epsilon, the fuzzy comparison predicates are defined
    in section 4.2.2 (Accuracy of floating point arithmetic) of
    Knuth, The Art of Computer Programming, vol 2, Seminumerical Algorithms
    (2nd edition) on page 218.

    (21)  'fuzzy <'(U, V) <->  V-U  >  epsilon.b^max(e_u, e_v)
    (22)  'fuzzy ~'(U, V) <-> |V-U| =< epsilon.b^max(e_u, e_v)
    (23)  'fuzzy >'(U, V) <->  U-V  >  epsilon.b^max(e_u, e_v)
    (24)  'fuzzy ='(U, V) <-> |V-U| =< epsilon.b^min(e_u, e_v)

    where U = F.b^e_u and |F| < 1
      and V = G.b^e_v and |G| < 1

The "fuzzvalue" can be set by the user.

---
	Peter Ludemann  +1-415-813-3800  ludemann@quintus.com