function - LISP:以谓词作为参数

Question

我想要一个谓词作为函数的参数。

(DEFUN per (F L)
    (cond ((F L) 'working)
          (T     'anything)))

(per 'numberp 3)

结果它引发了一个错误:

Undefined operator F in form (F L).

Answer 1

如 Technical Issues of Separation in Function Cells and Value Cells 中所述,Common Lisp 是 Lisp-2，也就是说，你需要funcall :

(defun per (F L)
  (if (funcall F L)
      'working
      'other))
(per #'numberp 3)
==> WORKING
(per #'numberp "3")
==> OTHER

另见 apply .