lispdoc - results for constantly

(constantly value)
Function: Return a function that always returns VALUE.
Example:
(defun compute-warning-handler (handle-warnings)
  (let ((nothing (constantly nil)))
    (ecase handle-warnings
      ((t) #'show-warning)
      (:debug #'debug-warning)
      ((nil) nothing))))
Mentioned in:
HyperSpec - Function CONSTANTLY