K& R练习

2006年4月12日13： 18:44 -0700，mdh < MD ** @ comcast.net>写道：

On 12 Apr 2006 13:18:44 -0700, "mdh" <md**@comcast.net> wrote:

不寻找答案，但更多的解释。
...
功能将标签扩展到空白（取决于标签的位置>与下一个制表符的关系）。我一直在努力理解
为什么会这样做....为什么不单独留下标签。

Not looking for an answer, but more of an explanation.
...
function to expand the tabs to blanks ( depending upon where the tab is
in relationship to the next tab-stop). I have been trying to understand
why one would do this....why not just leave the tabs alone.

< off-topic>

简单：


（a）有些设备（打印机）不处理标签 - 他们可能会忽略

，或只打印在现代计算机/操作系统中，

打印机驱动程序将自动执行选项卡扩展，但对于

其他设备，您需要将其作为单独的步骤执行。


（b）我在代码中使用4列制表位。我的一些同事使用3

或8.（是的，我们应该有编码标准，但这是一个单独的故事）代码在某人身上仔细而精美地格式化's
屏幕，当有人在他/她的编辑器中使用不同的

默认设置查看它时看起来很糟糕。除非您使用空格而不是

标签。

< / off-topic>

<off-topic>
Simple:

(a) Some devices (printers) do not process tabs - They may ignore
them, or print only one space, etc. In a modern computer/OS the
printer driver will perform the tab expansion automatically, but for
other devices you need to do it as a separate step.

(b) I use 4 column tab stops in my code. Some of my colleagues use 3
or 8. (Yes, we should have coding standards for that, but that is a
separate story) Code carefully and beautifully formatted in somebody''s
screen, looks terrible when somebody looks at it with different
default settings in his/her editor. Unless you use spaces instead of
tabs.
</off-topic>

Roberto Waltman写道：

Roberto Waltman wrote:

简单：

< OT>


谢谢Roberto ......是的......我意识到文字有点老......但是它确实是回到主人身上的一种刺激。


感谢您的解释。


< OT>

<OT>

thank you Roberto...yes...I realize that the text is a bit old...but it
sure is a thrill to go back to the masters.

Thanks for that explantation.

<OT>

mdh写道：

不是寻找答案，而是更多的解释。回想那些你有时间做这些令人兴奋的日子，我可以问这个。

练习1-22要求程序折叠。在第n列之前将长输入线分成2或更短的线......等等现在，在网上和C答案簿中有许多答案，其中包括
函数将选项卡扩展为空白（取决于选项卡与下一个制表符相关的位置）。我一直在努力理解
为什么会这样做....为什么不单独留下标签。

Not looking for an answer, but more of an explanation. Thinking back
to those heady days when you had the time to do them, may I ask this.

Exercise 1-22 asks for a program to "fold" long input lines into 2 or
more shorter lines before the nth column... etc etc. Now, there are
numerous anwers on the web and in the "C answer book", which includes a
function to expand the tabs to blanks ( depending upon where the tab is
in relationship to the next tab-stop). I have been trying to understand
why one would do this....why not just leave the tabs alone.

在某些时候你会需要将标签转换为空格才能显示它们。这可能是终端或打印机的固件，

终端仿真器窗口的代码，或者

编辑器的显示功能。例如，以下来自NetBSD内核的摘录

终端处理代码将输出转换为空格

到一个无法自行处理标签的设备：


if（c ==''\'''&&

ISSET（oflag，OXTABS）&&！ISSET（ tp-> t_lflag，EXTPROC））{

c = 8 - （tp-> t_column& 7）;

notout = b_to_q（""，c ，& tp-> t_outq）;


-

Diomidis Spinellis

代码质量：开源视角（ Addison-Wesley 2006）
http://www.spinellis.gr/codequality