NAME
pow, powf, powl - power functions SYNOPSIS
#include
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 featuretestmacros(7)): powf(), powl(): BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 || ISOC99SOURCE || POSIXCSOURCE >= 200112L;
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 HUGEVAL, HUGEVALF, or HUGEVALL, respectively, with the mathemati‐ cally 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 infin‐ ity, 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 infin‐ ity, 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 HUGEVAL, HUGEVALF, or HUGEVALL, 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 +HUGEVAL, +HUGEVALF, or +HUGEVALL, is returned. ERRORS See matherror(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 (FEINVALID) is raised. Pole error: x is zero, and y is negative
errno is set to ERANGE (but see BUGS). A divide-by-zero float‐
ing-point exception (FEDIVBYZERO) is raised. Range error: the result overflows
errno is set to ERANGE. An overflow floating-point exception (FEOVERFLOW) is raised. Range error: the result underflows
errno is set to ERANGE. An underflow floating-point exception (FEUNDERFLOW) is raised. ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌─────────────────────────┬───────────────┬─────────┐ │Interface │ Attribute │ Value │ ├─────────────────────────┼───────────────┼─────────┤
│pow(), powf(), powl() │ Thread safety │ MT-Safe │ └─────────────────────────┴───────────────┴─────────┘ CONFORMING TO
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89. BUGS In glibc 2.9 and earlier, when a pole error occurs, errno is set to
EDOM instead of the POSIX-mandated ERANGE. Since version 2.10, glibc does the right thing. 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
(FEINVALID) 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 excep‐ tion (FEINVALID) in addition to the overflow or underflow exception. SEE ALSO cbrt(3), cpow(3), sqrt(3) COLOPHON
This page is part of release 3.53 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/.
2010-09-12 POW(3)