Major Section: SWITCHES-PARAMETERS-AND-MODES
Examples: ACL2 !>(invisible-fns-table (w state)) ((binary-+ unary--) (binary-* unary-/) (unary-- unary--) (unary-/ unary-/))Among other things, the setting above has the effect of making
unary--``invisible'' for the purposes of applying permutative
binary-+trees. Also see add-invisible-fns, see remove-invisible-fns, and see set-invisible-fns-table.
See table for a general discussion of tables.
The ``invisible functions table'' is an alist with elements of the following
fn is a function symbol and the
ufni are unary function
symbols in the current ACL2 world, and
k is at least 1.
(fn ufn1 ufn2 ... ufnk)
This table thus associates with certain function symbols, e.g.,
above, a set of unary functions, e.g., the
ufni above. The
fn in the invisible functions table are said to be
``invisible with respect to
fn is not the
car of any
pair in the
alist, then no function is invisible for it. Thus for
example, setting the invisible functions alist to
eliminates the consideration of invisibility.
The notion of invisibility is involved in the use of the
loop-stopper field of
rewrite rules to prevent the indefinite
application of permutative rewrite rules. Roughly speaking, if
rewrite rules are being used to permute
arg and (ufni arg) inside of
a nest of
fn calls, and
ufni is invisible with respect to
(ufni arg) are considered to have the same ``weight'' and
will be permuted so as to end up as adjacent tips in the