sbcl - 为什么不按顺序执行代码[重复]

Question

我正在删除书中的示例：ANSI Common Lisp，第 14.6 章条件。

sbcl 没有以正确的顺序打印提示：

示例代码：

(defun user-input (prompt)
    (format t prompt)
    (let ((str (read-line)))
      (or (ignore-errors (read-from-string str))
      nil)))

在sbcl测试中，提示不会按顺序打印：

* (defun user-input (prompt)
    (format t prompt)
    (let ((str (read-line)))
      (or (ignore-errors (read-from-string str))
      nil)))

STYLE-WARNING: redefining COMMON-LISP-USER::USER-INPUT in DEFUN

USER-INPUT
* (user-input "Please type an expression> ")
test
Please type an expression> 
TEST
* (user-input "Please type an expression> ")
#%@#+!!
Please type an expression> 
NIL
* 

但在 clisp 中，提示是按顺序打印的，并且按预期工作：

[5]> (defun user-input (prompt)
    (format t prompt)
    (let ((str (read-line)))
      (or (ignore-errors (read-from-string str))
You are in the top-level Read-Eval-Print loop.
Help (abbreviated :h) = this list
Use the usual editing capabilities.
(quit) or (exit) leaves CLISP.
  nil)))
USER-INPUT
[6]> (user-input "Please type an expression> ")
Please type an expression> #%@#+!!
NIL
[7]> 

Answer 1

在后面插入force-output format 在您的 user-input 中以避免 i/o 缓冲问题： 通常，在换行符或 force-output 或 finish-output。