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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN"><!-- This collection of hypertext pages is Copyright 1995-2005 by Steve Summit. --><!-- Content from the book "C Programming FAQs: Frequently Asked Questions" --><!-- (Addison-Wesley, 1995, ISBN 0-201-84519-9) is made available here by --><!-- permission of the author and the publisher as a service to the community. --><!-- It is intended to complement the use of the published text --><!-- and is protected by international copyright laws. --><!-- The on-line content may be accessed freely for personal use --><!-- but may not be published or retransmitted without explicit permission. --><!-- --><!-- this page built Sat Dec 24 21:47:47 2005 by faqproc version 2.7 --><!-- from source file miscbits.sgml dated Wed Dec 21 13:02:12 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/misc/sd27.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 08:02:52 GMT --><head><meta name=GENERATOR content="faqproc"><link href="http://www.eskimo.com/notfound.html" rev=subdocument><title></title></head><body bgcolor="#ffffff"> <a href="../index-2.html"><img src="../images/buttontop.gif" alt="top/contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><hr>[This was posted by Alan Watson back in 1996,passing on a suggestion by Mark Brader.Dik Winter believes that the original idea was due to Karl Heuer.]<br><br>For this purpose, probably the best thing is some creative use of macros.(I wish I could remember who invented this little trick.) You can writethe 16-bit binary number 1100110011110000 as<pre> B16( X X O O X X O O X X X X O O O O )</pre>if you first define<pre> #define X <<1)+1 #define O <<1) /* the argument of B16 must be a total of 16 occurrences of one or the other of the above two macros, effectively expressing a number in binary */ #define B16(arg) (((((((((((((((((0 arg)</pre> For visual purposes it may be even better to use _ as the name for thezero-bit, rather than O; but there's a loss of portability then, sincethe identifier _ is in the C implementation's name space and thereforemay be used for some purpose in some implementations. Another goodchoice would be o, which suggests 0 without looking quite so much like it.<br><br>If you're using an unsigned type for the bitmap, as one normally should,then cast the 0 to that type inside the definition of the macro B16.<hr><p><a href="base2.html" rev=subdocument>back</a></p><hr><p><a href="../questions.html"><img src="../images/buttontop.gif" alt="contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><br><a href="../about.html">about this FAQ list</a> <a href="../eskimo.html">about eskimo</a> <a href="../search.html">search</a> <a href="../feedback.html">feedback</a> <a href="copyright.html">copyright</a><p>Hosted by<a href="http://www.eskimo.com/"><img src="../../www.eskimo.com/img/link/eskitiny.gif" alt="Eskimo North"></a></p></body><!-- Mirrored from c-faq.com/misc/sd27.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 08:02:52 GMT --></html>⌨️ 快捷键说明
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