+
+;;; Compile a version of BODY for all TYPES, and dispatch to the
+;;; correct one based on the value of VAR. This was originally used
+;;; only for strings, hence the name. Renaming it to something more
+;;; generic might not be a bad idea.
+(defmacro string-dispatch ((&rest types) var &body body)
+ (let ((fun (gensym "STRING-DISPATCH-FUN-")))
+ `(flet ((,fun (,var)
+ ,@body))
+ (declare (inline ,fun))
+ (etypecase ,var
+ ,@(loop for type in types
+ collect `(,type (,fun (the ,type ,var))))))))
+