RE: CMSC771 - uninstantiated arithmetic expressions


csaba1 (csaba1@umbc.edu)
Tue, 18 Mar 2003 12:24:35 -0500


Hello,

This may not be of much help, but I tried the following in xsb:

foo(X) :- A=X,B=4,A>B.

.. as long as I call it like foo(5).

If I call it with foo(X) I get the following error:

++Error[XSB]: [Runtime/C] Uninstantiated argument of evaluable function -/2
   Goal: _Var - 44444, probably as 2nd arg of is/2
! Aborting...

I think your variable A or B is not getting instantiated, and that of course
will depend on what clause1 or clause2 looks like.

Csaba

>===== Original Message From Tom Armstrong <arm1@coral.cs.umbc.edu> =====
>Here's my naive question of the day:
>
>I want to make a comparison between two initially uninstantiated
>variables. Take the rule to be foo(X) :- A=clause1,B=clause2,A>B., say.
>XSB doesn't care for my attempt and tells me about it.
>
>The closest documentation I can find is in the constraint solving section.
>Interestingly, their sample code doesn't perform as they claim on my
>installation nor cs.
>
>tom.



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