infnan(3) [linux man page]
INFNAN(3) Linux Programmer's Manual INFNAN(3) NAME
infnan - deal with infinite or not-a-number (NaN) result SYNOPSIS
#include <math.h> double infnan(int error); Link with -lm. DESCRIPTION
The infnan() function returns a suitable value for infinity and "not-a-number" (NaN) results. The value of error can be ERANGE to repre- sent infinity or anything else to represent NaN. errno is also set. RETURN VALUE
If error is ERANGE (Infinity), HUGE_VAL is returned. If error is -ERANGE (-Infinity), -HUGE_VAL is returned. If error is anything else, NAN is returned. ERRORS
EDOM The value of error is "not-a-number" (NaN). ERANGE The value of error is positive infinity or negative infinity. CONFORMING TO
4.3BSD. NOTES
This obsolete function was provided in libc4 and libc5, but is not available in glibc2. GNU
1993-06-02 INFNAN(3)
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POW(3) Linux Programmer's Manual POW(3) NAME
pow, powf, powl - power functions SYNOPSIS
#include <math.h> double pow(double x, double y); float powf(float x, float y); long double powl(long double x, long double y); Link with -lm. Feature Test Macro Requirements for glibc (see feature_test_macros(7)): powf(), powl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99 DESCRIPTION
The pow() function returns the value of x raised to the power of y. RETURN VALUE
On success, these functions return the value of x to the power of y. If x is a finite value less than 0, and y is a finite noninteger, a domain error occurs, and a NaN is returned. If the result overflows, a range error occurs, and the functions return HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with the mathemat- ically correct sign. If result underflows, and is not representable, a range error occurs, and 0.0 is returned. Except as specified below, if x or y is a NaN, the result is a NaN. If x is +1, the result is 1.0 (even if y is a NaN). If y is 0, the result is 1.0 (even if x is a NaN). If x is +0 (-0), and y is an odd integer greater than 0, the result is +0 (-0). If x is 0, and y greater than 0 and not an odd integer, the result is +0. If x is -1, and y is positive infinity or negative infinity, the result is 1.0. If the absolute value of x is less than 1, and y is negative infinity, the result is positive infinity. If the absolute value of x is greater than 1, and y is negative infinity, the result is +0. If the absolute value of x is less than 1, and y is positive infinity, the result is +0. If the absolute value of x is greater than 1, and y is positive infinity, the result is positive infinity. If x is negative infinity, and y is an odd integer less than 0, the result is -0. If x is negative infinity, and y less than 0 and not an odd integer, the result is +0. If x is negative infinity, and y is an odd integer greater than 0, the result is negative infinity. If x is negative infinity, and y greater than 0 and not an odd integer, the result is positive infinity. If x is positive infinity, and y less than 0, the result is +0. If x is positive infinity, and y greater than 0, the result is positive infinity. If x is +0 or -0, and y is an odd integer less than 0, a pole error occurs and HUGE_VAL, HUGE_VALF, or HUGE_VALL, is returned, with the same sign as x. If x is +0 or -0, and y is less than 0 and not an odd integer, a pole error occurs and +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL, is returned. ERRORS
See math_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur: Domain error: x is negative, and y is a finite noninteger errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised. Pole error: x is zero, and y is negative errno is set to ERANGE (but see BUGS). A divide-by-zero floating-point exception (FE_DIVBYZERO) is raised. Range error: the result overflows errno is set to ERANGE. An overflow floating-point exception (FE_OVERFLOW) is raised. Range error: the result underflows errno is set to ERANGE. An underflow floating-point exception (FE_UNDERFLOW) is raised. CONFORMING TO
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89. BUGS
For a pole error, errno is set to EDOM; POSIX.1 says it should be set to ERANGE. If x is negative, then large negative or positive y values yield a NaN as the function result, with errno set to EDOM, and an invalid (FE_INVALID) floating-point exception. For example, with pow(), one sees this behavior when the absolute value of y is greater than about 9.223373e18. In version 2.3.2 and earlier, when an overflow or underflow error occurs, glibc's pow() generates a bogus invalid floating-point exception (FE_INVALID) in addition to the overflow or underflow exception. SEE ALSO
cbrt(3), cpow(3), sqrt(3) COLOPHON
This page is part of release 3.25 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/. 2008-08-10 POW(3)