- boolean? Xprocedure
- procedure? Xprocedure
- port? Xprocedure
- string? Xprocedure
- vector? Xprocedure
- number? Xprocedure
- exact? Xprocedure
- inexact? Xprocedure
- rational? Xprocedure
- real? Xprocedure
- complex? Xprocedure
- exact-integer? Xprocedure
- bytevector? Xprocedure
Type predicates.