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    • Op-funct

    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.