Ops1 declares an enumeration type of the unary operators of the MiniC language (this makes is flexible to add operators). Available operators are:

• NotB: a bitwise negation of Cbool values.
• CastB: instructs the type checker to interpret this machine word as boolean, i.e., make it a Cbool value.
• CastN: instructs the type checker to interpret this machine word as Cnat, i.e., make it a Cnat value.
• CastZ: instructs the type checker to interpret this machine word as Cint, i.e., make it a Cint value.

Note that cast operators do not change the machine word, but due to the different interpretation, the value might still change (since Cint interprets machine words using 2-complement while Cnat uses radix-2).