FLI type descriptor
enum. fli
:enum &rest enum-constants
enum-constants ::= {symbol | (symbol value)}*
A sequence of one or more symbols naming the elements of the enumeration.
A symbol naming an element of the enumeration.
An integer specifying the index of symbol.
:enum type converts between a Lisp list and the Cenum type. Each entry in the enum-constants can either consist of a symbol, in which case the first entry has an index value of 0, or of a list of a symbol and its corresponding index value. define-c-enum, page 43, for an example using the:enum type. define-c-enum