Search the FAQ Archives

3 - A - B - C - D - E - F - G - H - I - J - K - L - M
N - O - P - Q - R - S - T - U - V - W - X - Y - Z
faqs.org - Internet FAQ Archives

FAQ: Lisp Frequently Asked Questions 3/7 [Monthly posting]
Section - [3-0] Why does (READ-FROM-STRING "foobar" :START 3) return FOOBAR instead of BAR?

( Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Single Page )
[ Usenet FAQs | Web FAQs | Documents | RFC Index | Business Photos and Profiles ]


Top Document: FAQ: Lisp Frequently Asked Questions 3/7 [Monthly posting]
Previous Document: News Headers
Next Document: [3-1] Why can't it deduce from (READ-FROM-STRING "foobar" :START 3) that the intent is to specify the START keyword parameter rather than
See reader questions & answers on this topic! - Help others by sharing your knowledge

READ-FROM-STRING is one of the rare functions that takes both &OPTIONAL and
&KEY arguments:

       READ-FROM-STRING string &OPTIONAL eof-error-p eof-value 
                               &KEY :start :end :preserve-whitespace

When a function takes both types of arguments, all the optional
arguments must be specified explicitly before any of the keyword
arguments may be specified.  In the example above, :START becomes the
value of the optional EOF-ERROR-P parameter and 3 is the value of the
optional EOF-VALUE parameter.
     
To get the desired result, you should use
   (READ-FROM-STRING "foobar" t nil :START 3)
If you need to understand and use the optional arguments, please refer
to CLTL2 under READ-FROM-STRING, otherwise, this will behave as
desired for most purposes.

User Contributions:

Comment about this article, ask questions, or add new information about this topic:

CAPTCHA