define-c-union name &rest slot-descriptions => list
slot-descriptions
::= {
slot-name
| (
slot-name
slot-type
)}*
The name of the new union type descriptor.
A sequence of symbols, possibly with type descriptions, naming the slots of the union.
A symbol naming the slot.
The FLI type of the slot.
The macro
define-c-union
is used to define an FLI union type specifier, which corresponds to the C
union
type. It is a convenience function, as a union type could also be defined using define-foreign-type.
A union is an aggregate type, or collection, of other FLI types. The types contained in a union are referred to as slots, and can be accessed using the foreign-slot-type and foreign-slot-value functions.
In the following example a union is defined using
define-c-union
, and the corresponding C code is given.
(fli:define-c-union a-point (x :int)
(color :byte)
(ident :char))
union a-point {
int x;
byte color;
char ident;
};