Add a new custom keyword hint
(add-custom-keyword-hint :my-hint (my-hint-fn val ...))
(my-hint-fn val ...)
:checker (my-hint-checker-fn val ...))
(add-custom-keyword-hint :key term1 :checker term2)
where :key is a keywordp not among the primitive keyword hints
listed in *hint-keywords*, the :checker argument is optional, and
term1 and (if supplied) term2 are terms with certain free-variable
and signature restrictions described below. Henceforth, :key is treated
as a custom keyword hint, e.g., the user can employ :key in hints to
defthm, such as:
(defthm name ...
:hints (("Subgoal *1/1'" ... :key val ...))).
Custom keyword hints are complicated. To use them you must understand
state, multiple values (e.g., mv and mv-let), ACL2's
notion of error triples (see programming-with-state), how to generate
``soft'' errors with er, how to use fmt-strings to control
output, how to use computed hints (see computed-hints) and some aspects
of ACL2's internal event processing. Furthermore, it is possible to implement
a custom keyword hint that can make an event non-reproducible! So we
recommend that these hints be developed by ACL2 experts. Basically the custom
keyword feature allows the implementors and other experts to extend the hint
facility without modifying the ACL2 sources.
Term1 is called the ``generator'' term and term2 is called the
``checker'' term of the custom keyword hint :key. Together they specify
the semantics of the new custom keyword hint :key. Roughly speaking,
when a custom keyword hint is supplied by the user, as in
(defthm name ...
:hints (("Subgoal *1/1'" ... :my-hint val ...))).
the checker term is evaluated on val to check that val is of the
expected shape. Provided val passes the check, the generator term is
used to compute a standard hint. Like computed hints, the generator of a
custom keyword hint is allowed to inspect the actual clause on which it
is being fired. Indeed, it is allowed to inspect the entire list of hints
(standard and custom) supplied for that clause. Thus, in the most general
case, a custom keyword hint is just a very special kind of computed hint.
The generator, term1, must have no free variables other than:
id clause world stable-under-simplificationp
hist pspv ctx state).
Moreover, either term1 must evaluate to a single non-stobj
value, or else it must be single-threaded in state and have the standard
error-triple output signature, (mv * * state).
The restrictions on the checker, term2, are that it be single-threaded
in state, have the standard error-triple output signature, (mv * *
state), and have no free variables other than:
(val world ctx state).
For examples, see the community books directory books/hints/, in
To delete a previously added custom keyword hint, see remove-custom-keyword-hint.
The community book hints/merge-hint.lisp can be useful in writing
custom keyword hints. See the examples near the of the file.
Note: This is an event! It does not print the usual event summary
but nevertheless changes the ACL2 logical world and is so