公共列表:在不同的包中使用handler-case

Question

我有以下lisp代码:

;;; hop.lisp

(defpackage #:hop
  (:use #:cl ))

(in-package :hop)
(export 'hop)

(defun hop ()
  (restart-case
      (error "Hop")
    (hop ()
      (format t "hop"))))

我定义一个总是失败但提供重启的虚函数:hop.

在另一个包中,在此文件中:

;;; hip.lisp

(defpackage #:hip
  (:use #:cl #:hop))

(in-package :hip)

(defun dhip ()
  (hop:hop))

(defun hip ()
  (handler-case
      (hop:hop)
    (error (e)
      (declare (ignore e))
      (format t "restarts: ~a~%" (compute-restarts))
      (invoke-restart 'hop))))

我定义了从第一个包中调用函数(hop)的函数(hip)和(dhip).

当我打电话(dhip)时,sbcl给我一个提示,我可以选择使用我的重启跃点重新启动:

Hop
   [Condition of type SIMPLE-ERROR]

Restarts:
 0: [HOP] HOP
 1: [RETRY] Retry SLIME REPL evaluation request.
 2: [*ABORT] Return to SLIME's top level.
 3: [ABORT] abort thread (#<THREAD "repl-thread" RUNNING     {1009868103}>)

Backtrace:
  0: (HOP)
  1: (DHIP)
  2: (SB-INT:SIMPLE-EVAL-IN-LEXENV (DHIP) #<NULL-LEXENV>)
  3: (EVAL (DHIP))
--more--

这是我的预期.

但是,当我打电话(臀部)时,我的重启跃点没有列出(计算重启),并且它无法使用它:(

No restart HOP is active.
   [Condition of type SB-INT:SIMPLE-CONTROL-ERROR]

Restarts:
 0: [RETRY] Retry SLIME REPL evaluation request.
 1: [*ABORT] Return to SLIME's top level.
 2: [ABORT] abort thread (#<THREAD "repl-thread" RUNNING    {1009868103}>)

Backtrace:
  0: (SB-INT:FIND-RESTART-OR-CONTROL-ERROR HOP NIL T)
  1: (INVOKE-RESTART HOP)
  2: ((FLET #:FUN1 :IN HIP) #<unused argument>)
  3: (HIP)
  4: (SB-INT:SIMPLE-EVAL-IN-LEXENV (HIP) #<NULL-LEXENV>)
  5: (EVAL (HIP))

你知道怎么做可以使这个工作吗？

谢谢,

Guillaule

Answer 1

这与包无关.

使用HANDLER-CASE,当处理程序运行时,堆栈已经解开.因此,在函数中建立的重启已经消失.

请改用HANDLER-BIND.它在错误的上下文中运行处理程序,因此可以重新启动该函数.

例:

(defun hip ()
  (handler-bind ((error (lambda (e)
                          (declare (ignore e))
                          (format t "restarts: ~a~%" (compute-restarts))
                          (invoke-restart 'hop))))
      (hop)))