1.3 Type identifiers

A type identifier is a bound syntactic identifier whose syntactic binding’s descriptor contains informations about the type’s properties. Examples of type identifiers are:

• Struct–type name identifiers defined by define-struct; they are automatically made type identifiers by Vicare.
• Record–type name identifiers defined by define-record-type; they are automatically made type identifiers by Vicare. Condition object types (like &i/o) are special cases of these.
• The library (vicare) exports a set type identifiers (whose implementation is integrated in Vicare’s expander) representing the types of built–in objects. Some of them are: <fixnum>, <string>, <vector>, <textual-input-port>. Built-in object types.

Type identifiers are organised in a tree hierarchy, with subtypes inheriting properties of supertypes; by convention, <top> is the parent of all the type annotations, the root of the tree; <top> has no parent.

Many predefined type identifiers have names enclosed in “angular parentheses” ‘< >’, but this is just a convention. Any valid Scheme symbol can be used as name for a type identifier.