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Asgop

Asgop-case

Case macro for the different kinds of asgop 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 asgop structure, or to split into cases based on its type.

Short Form

In its short form, asgop-case allows you to safely check the type of a asgop structure. For example:

(asgop-case x :asg)

is essentially just a safer alternative to writing:

(equal (asgop-kind x) :asg)

Why is using asgop-case safer? When we directly inspect the kind with equal, there is no static checking being done to ensure that, e.g., :asg is a valid kind of asgop structure. That means there is nothing to save you if, later, you change the kind keyword for this type from :asg to something else. It also means you get no help if you just make a typo when writing the :asg symbol. Over the course of developing VL, we found that such issues were very frequent sources of errors!

Long Form

In its longer form, asgop-case allows you to split into cases based on the kind of structure you are looking at. A typical example would be:

(asgop-case x
  :asg ...
  :asg-add ...
  :asg-sub ...
  :asg-mul ...
  :asg-div ...
  :asg-rem ...
  :asg-pow ...
  :asg-shl ...
  :asg-shr ...
  :asg-bitand ...
  :asg-bitior ...
  :asg-bitxor ...
  :asg-and ...
  :asg-or ...)

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 :asg case, you can use fty::defprod-style foo.bar style accessors for x without having to explicitly add a asg b* binder.