emacs+slime+sbcl 单步调试

(defun next (x y) (/ (+ x y) 2))
(defun square (x) (* x x))


(defun sqrt-r(a b x)
  (declare (optimize
            (debug 3)
            (speed 0)
            (space 0)
            (compilation-speed 0)
            (safety 3)))
  (format t "~A ~A ~A~%" a b x)
  (let ((nex (next a b)))
    (new-if (< (- b a) 0.00001)
             nex
             (if (> (square nex) x)
                 (sqrt-r a nex x)
                 (sqrt-r nex b x)))))

(defun new-if (predicate then-clause else-clause)
  (cond (predicate then-clause)
        (t else-clause)))


(step (sqrt-r 1.0 2.0 2.0))

    这段程序会无限循环。要单步调试，需要加入下面这段程序，才能进入单步调试。

(declare (optimize
            (debug 3)
            (speed 0)
            (space 0)
            (compilation-speed 0)
            (safety 3)))

在emacs中,输入C-x e，然后s是单步调试，v是查看程序运行到的源程序部分。其他命令C-h m就行了。