slot-exists-p
object slot-name => generalized-boolean
object--an object.
slot-name--a symbol.
generalized-boolean--a generalized boolean.
Returns true if the object has a slot named slot-name.
defclass, defstruct
Although no implementation is required to do so, implementors are strongly encouraged to implement the function slot-exists-p using the function slot-exists-p-using-class described in the Metaobject Protocol.