class
DB.datatype class
Datatype for classifying theory elements.
Many of the functions in the DB
structure return answers
that involve the class
type, which is declared as
datatype class = Thm | Axm | Def
When occurring with th
, an ML value of type
thm
, Axm
means that th
has been
asserted as an axiom; Def
means that th
is a
constant definition; and Thm
means that th
is
a plain old theorem, i.e,. not an axiom or a definition.