NOTE-2-7-OTHER.html -- ACL2 Version 6.3

### NOTE-2-7-OTHER

ACL2 Version 2.7 Notes on Miscellaneous Changes

    Major Section:  NOTE-2-7

Made several minor documentation improvements. We are grateful to Eric Smith for suggesting (most of) these.

Improved `(show-bdd)` (see bdd) to give more useful feedback when there are ``leaf'' terms not known to be Boolean.

Sped up processing of large mutual-recursion nests. In one large example the speedup was roughly two orders of magnitude.

Modified event printing so that if both `'prove` and `'event` are inhibited, then events are no longer printed on behalf of `certify-book`, `encapsulate`, or `defstobj`. Thanks to Eric Smith for prompting consideration of such a change.

The following technical change was made to support `with-error-trace` and `wet` (see note-2-7-new-functionality), but may be of interest to those who do low-level programming using the ACL2 logical `world`. The `'unnormalized-body` property is now stored not only for functions defined in `:``logic` mode, but also for functions defined by the user in `:``program` mode. (`:Program` mode Functions built into ACL2 still have their `'unnormalized-body` property omitted, in order to save space.)

The handling of ``invisible'' functions for purposes of controlling rewriting (see loop-stopper) has been moved to a new table; see invisible-fns-table. Macros that access and modify this table are called ```...-invisible-fns-table`'' in place of their former names, ```...-invisible-fns-alist`.'' This feature was formerly implemented in the `acl2-defaults-table`, which prevented a book from exporting lists of invisible functions intended to work with the rewrite rules developed in the book. Thanks to Eric Smith and Rob Sumners for suggesting this change. See set-invisible-fns-table (formerly `set-invisible-fns-alist`), and also see add-invisible-fns and see remove-invisible-fns, which provides ways to incrementally add to and remove from this table, respectively. The handling of printing binary function call nests using macros (See add-binop) has also been moved out of the `acl2-defaults-table` as suggested by Eric and Rob, but this feature didn't work anyhow (see note-2-7-bug-fixes). Incidentally, the symbols `binop-table`, `add-binop`, and `remove-binop` have all been added to the list `*acl2-exports*` (see acl2-user), `add-invisible-fns` and `remove-invisible-fns` have been added to that list, and `set-invisible-fns-alist` has been replaced in that list by `set-invisible-fns-table`. Function `invisible-fns-alistp` is no longer defined and has been removed from `*acl2-exports*`.

We now enforce the stated restriction on the pairings in `macro-aliases-table` (see macro-aliases-table), namely, that it associates names of macros with names of funcions (with respect to the current ACL2 logical world). We make a similar requirement on `invisible-fns-table`.

The `theory-invariant` event has been modified so that the default action is an error rather than a warning. Thanks to Eric Smith for suggesting this change. Also, the value returned upon successful execution of a `theory-invariant` event is now the key.

Proof output that reports destructor elimination no longer uses the word ``generalizing''. This small change may help in browsing proof output, since now ``generaliz'' takes you to true uses of generalization. Thanks to Matyas Sustik for suggesting such a change.

The command `:``pl` now prints an abbreviated controller-alist for `;``definition` rules. Formerly the output from `:pl` could be overwhelming when the supplied function was part of a large `mutual-recursion` nest.

The defaults for keyword parameters of `certify-book` have changed. See note-2-7-bug-fixes, in particular, the discussion there of two modifications to `certify-book`.

Technical changes have been made to `compress1` and `compress2` that should usually be invisible to users. The next paragraph describes them in detail, only for competeness (i.e., that description can be ignored by most users). But first, here is an example showing an effect on users. The slow array warning was not there previously. Notice that the warning only arises if the event form is changed. The solution is to be sure that redundant `defconst` forms are syntactically identical.

    ACL2 !>(defconst *a* (compress1 'demo
                                    '((:header :dimensions (5)
                                               :maximum-length 15
                                               :default uninitialized
                                               :name demo)
                                      (1 . one)
                                      (0 . zero))))

    Summary
    Form:  ( DEFCONST *A* ...)
    Rules: NIL
    Warnings:  None
    Time:  0.00 seconds (prove: 0.00, print: 0.00, other: 0.00)
     *A*
    ACL2 !>(aref1 'demo *a* 0)
    ZERO
    ACL2 !>(defconst *a* (compress1 'demo
                                    '((:header :dimensions (5)
                                               :maximum-length 15
                                               :default uninitialized
                                               :name demo)
                                      (1 . one)
                                      (0 . zero))))

    This event is redundant.  See :DOC redundant-events.

    Summary
    Form:  ( DEFCONST *A* ...)
    Rules: NIL
    Warnings:  None
    Time:  0.00 seconds (prove: 0.00, print: 0.00, other: 0.00)
     :REDUNDANT
    ACL2 !>(aref1 'demo *a* 0)
    ZERO
    ACL2 !>(defconst *a* (compress1 'demo
                                    '((:header :dimensions (5)
                                               :maximum-length 15
                                               :default uninitialized
                                               :name demo)
                                      (0 . zero)
                                      (1 . one))))

    This event is redundant.  See :DOC redundant-events.

    Summary
    Form:  ( DEFCONST *A* ...)
    Rules: NIL
    Warnings:  None
    Time:  0.00 seconds (prove: 0.00, print: 0.00, other: 0.00)
     :REDUNDANT
    ACL2 !>(aref1 'demo *a* 0)

    **********************************************************
    Slow Array Access!  A call of AREF1 on an array named
    DEMO is being executed slowly.  See :DOC slow-array-warning
    **********************************************************

    ZERO
    ACL2 !>

As before, the von Neumann structure stored in the `'acl2-array` property of the array name contains the array list object in its `car`. However, previously it was the case that `compress1` and `compress2` did not update that `car` when its new value would be equal to its old value. This was done largely in support of some type-set tables defined using `defconst` in `type-set-b.lisp`. The new versions of `compress1` and `compress2` are simpler in that no such exception is made in the case of equal lists, although instead the entire compression process is short-circuited when the input array list object is `eq` to the `car` of the `'acl2-array` property. This change was made because the equality test was causing a ``slow array access'' warning to be printed in rare cases during proofs, as described elswhere (see note-2-7-bug-fixes).

We no longer distribute documentation specific to Lucid Emacs. The Info documentation in directory `doc/EMACS/` works well both for Gnu Emacs and XEmacs.

A little-advertised macro, `value`, has long been allowed for top-level forms in books; see embedded-event-form. This has been replaced by a new macro, `value-triple`. The two have the same semantics at the top-level of books, where `state` is ``live''. However, `value-triple` should be used at the top-level of a book, while `value` should be used in function definitions (as before). This change eliminates a warning put out by the Allegro Common Lisp compiler for top-level `value` forms in books.