Predicate type

A function type annotated with what it proves when returning true - e.g., (-> Any Boolean : mt) means "takes anything, returns Boolean, and when true, input was mt." Essentially, a type of a Type pred

A function type annotated with what it proves when returning true - e.g., (-> Any Boolean : mt) means "takes anything, returns Boolean, and when true, input was mt." Essentially, a type of a Type predicate.