printing - 输入字符串并将其打印回来的程序将不起作用

Question

我觉得应该是 Common Lisp 中的一段非常简单的代码，我想要它做的就是要求用户输入，然后将其打印回来。

这是我的代码(“之前”和“之后”的打印来自尝试调试，它显示出一些奇怪的东西。

(defun get-input (prompt)
    (clear-input)
    (write-string prompt)
    (finish-output)
    (read-line)
)

(let    (   
            (p1 (get-input "Enter: "))
        )
    (princ "Before")
    (princ p1)
    (princ "After")
)    

当我运行它时，我得到以下信息

This is SBCL 1.2.1, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses.  See the CREDITS and COPYING files in the
distribution for more information.

WARNING: the Windows port is fragile, particularly for multithreaded
code.  Unfortunately, the development team currently lacks the time
and resources this platform demands.
* (load "test.lisp")

Enter: This is my string.
AftereThis is my string.
T

如您所见，我的“Before”字符串甚至都没有打印出来，而我的“After”字符串末尾有一个奇怪的“e”？为什么我第一次运行该程序时它似乎要求输入？

如果有人能提供帮助，我将不胜感激。谢谢

Answer 1

我相信这就是正在发生的事情，顺序是:

1. 程序计算要绑定(bind)到 p1 的表达式；这会生成您的提示并读取您的输入
2. Then 它打印“Before”
3. 然后它打印 p1 的值，(我认为)末尾有一个回车符，以便下一个要打印的内容位于该行的开头
4. 然后打印“After”，覆盖“Before”的前 5 个字符