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From: "dgaur at cdotd dot ernet dot in" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug libc/5308] New: Integer division and Modulo for -ve values Date: Mon, 12 Nov 2007 10:35:00 -0000 [thread overview] Message-ID: <20071112103550.5308.dgaur@cdotd.ernet.in> (raw) The Modulo operation as specified in http://xenia.media.mit.edu/~bdenckla/thesis/texts/htthe/node13.html says that for a fraction like n/k which can be expressed as n/k = i + j/k the C division and mod operation should yeild n div k = i (integer part) n mod k = j (remainder part) For n +ve above is true For n -ve -n/k = -i + j/k -n div k = -i -n mod k = j (+ve remainder) But running a sample program on Redhat enterprise Linux EL4 with libc-2.3.4 gcc version 3.4.3 20041212 (Red Hat 3.4.3-9.EL4) #include <stdio.h> #include <stdlib.h> #include <math.h> int main() { int n,k,j; n=-3; k=8; j=(n/k); printf("\n n div k %d", j); j=(n%k); printf("\n n mod k %d", j); } gives following output for n = -3 k = 8 n div k 0 n mod k -3 though it should have been as per hypothesis proposed in http://xenia.media.mit.edu/~bdenckla/thesis/texts/htthe/node13.html n div k -1 n mod k 5 Which is correct? -- Summary: Integer division and Modulo for -ve values Product: glibc Version: 2.4 Status: NEW Severity: minor Priority: P3 Component: libc AssignedTo: drepper at redhat dot com ReportedBy: dgaur at cdotd dot ernet dot in CC: dgaur at cdotd dot ernet dot in,glibc-bugs at sources dot redhat dot com http://sourceware.org/bugzilla/show_bug.cgi?id=5308 ------- You are receiving this mail because: ------- You are on the CC list for the bug, or are watching someone who is.
next reply other threads:[~2007-11-12 10:35 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-11-12 10:35 dgaur at cdotd dot ernet dot in [this message] 2007-11-12 15:14 ` [Bug libc/5308] " drepper at redhat dot com
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