-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 10/8/10 13:48 , Michael Tiernan wrote: > ----- "Tom Limoncelli" <t...@whatexit.org> wrote: >> I see this in code now and then: >> 1<<16-1 > > Being just a system geek and not a professional programmer, I don't > understand why one would use that notation instead of the more obvious > variations of "0x8000"? > I understand that the compiler, at compile time (not run time) will figure > out that the programmer "meant" 0x8000 from that piece of code so the end > result is the same but it seems that for documentation purposes it'd be more > obvious to do it the other way. > Am I missing something?
I see it as a matter of self-documentation; "0x8000" suggests a magic number of some kind, which is probably related to bits or to hardware control, whereas "1<<(mumble)" explicitly says "this is a bit". (The former might be a bit *mask*, or not linked to particular bits at all, for example a value written to a control register where the register isn't documented at the bit level but only the acceptable values.) Also, the "1<<n" syntax helps when you are coding to a specification which describes things in terms of bit numbers (e.g. "bit 0 controls the transmit register"). - -- brandon s. allbery [linux,solaris,freebsd,perl] allb...@kf8nh.com system administrator [openafs,heimdal,too many hats] allb...@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.10 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkyv52wACgkQIn7hlCsL25WN4wCghwyD0hLGLaV8P4UDUXtOj1S8 KCsAoK4S6h/DBs4G7pp/WDRKkds844wn =/va/ -----END PGP SIGNATURE----- _______________________________________________ Tech mailing list Tech@lopsa.org http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
