Op-funct-case
Case macro for the different kinds of op-funct 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 op-funct structure, or to split
into cases based on its type.
Short Form
In its short form, op-funct-case allows you to safely check the type of
a op-funct structure. For example:
(op-funct-case x :add)
is essentially just a safer alternative to writing:
(equal (op-funct-kind x) :add)
Why is using op-funct-case safer? When we directly inspect the
kind with equal, there is no static checking being done to
ensure that, e.g., :add is a valid kind of op-funct structure. That means there is nothing to save you
if, later, you change the kind keyword for this type from :add to something else. It also means you get no help
if you just make a typo when writing the :add
symbol. Over the course of developing VL, we found that such
issues were very frequent sources of errors!
Long Form
In its longer form, op-funct-case allows you to split into cases based
on the kind of structure you are looking at. A typical example would be:
(op-funct-case x
:add ...
:sub ...
:slt ...
:sltu ...
:and ...
:or ...
:xor ...
:sll ...
:srl ...
:sra ...
:mul ...
:mulh ...
:mulhu ...
:mulhsu ...
:div ...
:divu ...
:rem ...
:remu ...)
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 :add case,
you can use fty::defprod-style foo.bar style accessors for x
without having to explicitly add a add b*
binder.
