Burke_et_al-NIL_Reference_Manual_0286-1984

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N II. Manual 295' Peripheral Utilities
28. Peripheral Utilities
This chapter will accumulate documentation on various minor utilities which are distributed
with I'lL. but which are not necessarily part of NIL proper.
28.1 The Predicate Simplifier
Nil offers a predicate simplifier. which simplifies l.lsp-format predicates into disjunctive nonnal
t{lfI11. This progr,lm was originally written hy I )eepak Kapur with thc help of Ramcsh Patil for
th~ PRO'I OSYS 1"'\1 'llItomatic programming project directed h) \Villi4lm Martin at ~v11T in the mid
1lJ70s. Since then. it has heen convened to lise ISH [4]. hrought lip in both liSP \1:\CIII:\F liSP
and '11. and imprm ed at a low levcl. The code for this is not loaded hy dcf~Hl1t in '": it
exists as nil$disk:[nil.utilities]simp. and to load it. the package definition file
nil$disk:[nil.utilities]simp.pkg should he loaded first. This may he perflmned
automatically by use of
( r e qui r e 's imp)
See require. page 123.
This simplifier only really works on simple predicatcs and connectives. It perfonns some
trivial canonicalizations of arithmetic operations and inequalities (equal. greaterp. and lessp), but
it does not truly recognize identities or other relations among them. There is also a read-time
(compile-time) conditionalization for whether it attempts to deal with existential quantification. as
r('nr('c('''tt.,.t
·-r·--- ..··_- h"
......
f"rnlC Ilf th,.. ft,\rnl
J ."'..................- " ..."." ••
(for-some (kl k2 ... kll) pred)
This feature is nonnally turned off, which simplifies the internal dawstructures used and improves
the efficiency in the other cases. Again, simplification of fonns containing existcntial quantification
does not always reduce as well as it should. To get this one would have to recompile simp with
that feature turned on.
simp pred-fonn
Simplifies prcd-fonn. For example.
(simp '(and c d (or a b») =>
(or (and a c d) (and bed»
s1mpor pI p2
s impand pi p2
Approximately equivalent to
(s imp (1 is t and-or-or pI p2»
s 1mpnot pred
Simplifies the not of pred.
simp 0 r 11 s t pred-Iist
S 1mpandl1 s t pred-list
Simplifies the or or and of pred-list.
MC:NILMAN;UTILS 15
23-DEC-83