Stmt-case
Case macro for the different kinds of stmt structures.
This is an ACL2::fty sum-type case macro,
typically introduced by fty::defflexsum or fty::deftagsum. It
allows you to safely check the type of a stmt structure, or to split
into cases based on its type.
Short Form
In its short form, stmt-case allows you to safely check the type of
a stmt structure. For example:
(stmt-case x :labeled)
is essentially just a safer alternative to writing:
(equal (stmt-kind x) :labeled)
Why is using stmt-case safer? When we directly inspect the
kind with equal, there is no static checking being done to
ensure that, e.g., :labeled is a valid kind of stmt structure. That means there is nothing to save you
if, later, you change the kind keyword for this type from :labeled to something else. It also means you get no help
if you just make a typo when writing the :labeled
symbol. Over the course of developing VL, we found that such
issues were very frequent sources of errors!
Long Form
In its longer form, stmt-case allows you to split into cases based
on the kind of structure you are looking at. A typical example would be:
(stmt-case x
:labeled ...
:compound ...
:expr ...
:null ...
:if ...
:ifelse ...
:switch ...
:while ...
:dowhile ...
:for ...
:goto ...
:continue ...
:break ...
:return ...)
It is also possible to consolidate ``uninteresting'' cases using
:otherwise.
For convenience, the case macro automatically binds the fields of x for
you, as appropriate for each case. That is, in the :labeled case,
you can use fty::defprod-style foo.bar style accessors for x
without having to explicitly add a labeled b*
binder.
