FPCLASSIFY(3) Linux Programmer's Manual FPCLASSIFY(3)[top]NAMEfpclassify, isfinite, isnormal, isnan, isinf - floating-point classifi‐ cation macrosSYNOPSIS#include <math.h> int fpclassify(x); int isfinite(x); int isnormal(x); int isnan(x); int isinf(x); Link withFeature Test Macro Requirements for glibc (see feature_test_macros(7)): fpclassify(), isfinite(), isnormal(): _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99 isnan(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE || _ISOC99_SOURCE; or cc -std=c99 isinf(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99-lm.DESCRIPTIONFloating point numbers can have special values, such as infinite or NaN. With the macro fpclassify(x) you can find out what type x is. The macro takes any floating-point expression as argument. The result is one of the following values: FP_NAN x is "Not a Number". FP_INFINITE x is either positive infinity or negative infinity. FP_ZERO x is zero. FP_SUBNORMAL x is too small to be represented in normalized format. FP_NORMAL if nothing of the above is correct then it must be a nor‐ mal floating-point number. The other macros provide a short answer to some standard questions. isfinite(x) returns a non-zero value if (fpclassify(x) != FP_NAN && fpclassify(x) != FP_INFINITE) isnormal(x) returns a non-zero value if (fpclassify(x) == FP_NORMAL) isnan(x) returns a non-zero value if (fpclassify(x) == FP_NAN) isinf(x) returns 1 if x is positive infinity, andif x is nega‐ tive infinity.-1CONFORMING TOC99, POSIX.1. For isinf(), the standards merely say that the return value is non-zero if and only if the argument has an infinite value.NOTESIn glibc 2.01 and earlier, isinf() returns a non-zero value (actually: 1) if x is positive infinity or negative infinity. (This is all that C99 requires.)SEE ALSOfinite(3), INFINITY(3), isgreater(3), signbit(3)COLOPHONThis page is part of release 3.22 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2008-08-07 FPCLASSIFY(3)

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