AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Oddity in ByteBuffer code?          AppletTalk.com Forum Index -> Java Language Programming View previous topic :: View next topic   Author Message Remon van Vliet Guest Posted: Thu May 19, 2005 3:29 pm    Post subject: Oddity in ByteBuffer code? Hello, A snippet from ByteBuffer.compareTo(), can anyone figure out what this code does? : if ((v1 != v1) && (v2 != v2)) // For float and double Thanks, just curious, Remon Back to top Eric Sosman Guest Posted: Thu May 19, 2005 3:46 pm    Post subject: Re: Oddity in ByteBuffer code? Remon van Vliet wrote: Quote: Hello, A snippet from ByteBuffer.compareTo(), can anyone figure out what this code does? : if ((v1 != v1) && (v2 != v2)) // For float and double The test produces `true' if both v1 and v2 are NaN. -- [email]Eric.Sosman (AT) sun (DOT) com[/email] Back to top Patricia Shanahan Guest Posted: Thu May 19, 2005 3:52 pm    Post subject: Re: Oddity in ByteBuffer code? Remon van Vliet wrote: Quote: Hello, A snippet from ByteBuffer.compareTo(), can anyone figure out what this code does? : if ((v1 != v1) && (v2 != v2)) // For float and double Thanks, just curious, Remon It looks like a Not-a-Number test. NaNs do not compare equal to anything, themselves included. However, sometimes it is desirable to treat all NaNs as being equal to each other, leading to tests for NaNs on both sides of a comparison. If that is what is meant then if (Double.isNaN(v1) && Double.isNaN(v2)) would be better style. It does the same test, but is self-documenting. The test does not seem to make sense in this context. I don't see any way v1 or v2 could be double or float, and all byte values compare equal to themselves. I think it may be a case of over-enthusiastic copy-paste from DoubleBuffer, which does need it. Patricia Back to top Chris Uppal Guest Posted: Thu May 19, 2005 4:59 pm    Post subject: Re: Oddity in ByteBuffer code? Patricia Shanahan wrote: Quote: The test does not seem to make sense in this context. I don't see any way v1 or v2 could be double or float, and all byte values compare equal to themselves. I think it may be a case of over-enthusiastic copy-paste from DoubleBuffer, which does need it. Or, from the comment at the head of the 1.5 version of the source: // -- This file was mechanically generated: Do not edit! -- // a case of a tool being misapplied. -- chris Back to top Patricia Shanahan Guest Posted: Thu May 19, 2005 7:09 pm    Post subject: Re: Oddity in ByteBuffer code? Chris Uppal wrote: Quote: Patricia Shanahan wrote: The test does not seem to make sense in this context. I don't see any way v1 or v2 could be double or float, and all byte values compare equal to themselves. I think it may be a case of over-enthusiastic copy-paste from DoubleBuffer, which does need it. Or, from the comment at the head of the 1.5 version of the source: // -- This file was mechanically generated: Do not edit! -- // a case of a tool being misapplied. That makes the non-use of Double.isNaN even worse, because there was premeditated intent to use the code in pure integer contexts, where it is likely to be read by people who might not instantly recognize the (v1 != v1) idiom. Patricia Back to top Chris Uppal Guest Posted: Fri May 20, 2005 2:18 pm    Post subject: Re: Oddity in ByteBuffer code? Patricia Shanahan wrote: Quote: That makes the non-use of Double.isNaN even worse, because there was premeditated intent to use the code in pure integer contexts, where it is likely to be read by people who might not instantly recognize the (v1 != v1) idiom. And not even an explanatory comment ("For float and double" doesn't count as explanatory in my book. It scarcely even counts as a comment -- even the famous "you are not expected to understand this" would have been better ;-) <sigh/> What is the world coming to...? -- chris Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AppletTalk.com Forum Index -> Java Language Programming All times are GMT Page 1 of 1   Jump to: Select a forum Java Newsgroups----------------Java DiscussionsWeb-based java games comp.lang.java 3D Graphics API's for Java Java: Support and criticism Java System Announcements comp.lang.java.api JavaBeans Java and CORBA Java and Databases comp.lang.java.developer Java GUI Toolkits Java Help comp.lang.java.javascript JVM, native methods and hardware comp.lang.java.misc Java Language Programming Security and Java comp.lang.java.setup Java Software Tools comp.lang.java.tech ibm.software.java.linux  Non-English Java Newsgroups----------------Java Language (German)Language Java (Français)Java (Italian)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.