Major Section: EVENTS
Example:
(in-theory (set-difference-theories
(universal-theory :here)
'(flatten (:executable-counterpart flatten))))
General Form:
(in-theory term :doc doc-string)
where term is a term that when evaluated will produce a theory
(see theories), and doc-string is an optional documentation
string not beginning with ``:Doc-Section ...''. Because no unique name
is associated with an in-theory event, there is no way we can store the
documentation string doc-string in our documentation
database. Hence, we actually prohibit doc-string from having the form
of an ACL2 documentation string; see doc-string.Except for the variable world, term must contain no free variables.
Term is evaluated with the variable world bound to the current
world to obtain a theory and the corresponding runic theory
(see theories) is then made the current theory. Thus,
immediately after the in-theory, a rule is enabled iff its rule name
is a member of the runic interpretation (see theories) of some
member of the value of term. See theory-functions for a list
of the commonly used theory manipulation functions.
Note that it is often useful to surround in-theory events with
local, that is, to use (local (in-theory ...)). This use of
local in encapsulate events and books will prevent the
effect of this theory change from being exported outside the context of that
encapsulate or book.
Also see hints for a discussion of the :in-theory hint, including some
explanation of the important point that an :in-theory hint will always be
evaluated relative to the current ACL2 logical world, not relative to
the theory of a previous goal.
In-theory returns an error triple (see error-triples). When the
return is without error, the value is of the form
(mv nil (:NUMBER-OF-ENABLED-RUNES k) state) where k is the length of
the new current theory. This value of k is what is printed when an
in-theory event evaluates without error at the top level.
