1POW(3) Linux Programmer's Manual POW(3)
2
6 pow, powf, powl - power functions
7
9 #include <math.h>
10 double pow(double x, double y);
12 float powf(float x, float y);
13 long double powl(long double x, long double y);
14 Link with -lm.
16 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
18 powf(), powl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
20 _ISOC99_SOURCE; or cc -std=c99
21
23 The pow() function returns the value of x raised to the power of y.
24
26 On success, these functions return the value of x to the power of y.
27 If x is a finite value less than 0, and y is a finite non-integer, a
29 domain error occurs, and a NaN is returned.
30 If the result overflows, a range error occurs, and the functions return
32 HUGE_VAL, HUGE_VALF, or HUGE_VALL, respectively, with the mathemati‐
33 cally correct sign.
34 If result underflows, and is not representable, a range error occurs,
36 and 0.0 is returned.
37 Except as specified below, if x or y is a NaN, the result is a NaN.
39 If x is +1, the result is 1.0 (even if y is a NaN).
41 If y is 0, the result is 1.0 (even if x is a NaN).
43 If x is +0 (-0), and y is an odd integer greater than 0, the result is
45 +0 (-0).
46 If x is 0, and y greater than 0 and not an odd integer, the result is
48 +0.
49 If x is -1, and y is positive infinity or negative infinity, the result
51 is 1.0.
52 If the absolute value of x is less than 1, and y is negative infinity,
54 the result is positive infinity.
55 If the absolute value of x is greater than 1, and y is negative infin‐
57 ity, the result is +0.
58 If the absolute value of x is less than 1, and y is positive infinity,
60 the result is +0.
61 If the absolute value of x is greater than 1, and y is positive infin‐
63 ity, the result is positive infinity.
64 If x is negative infinity, and y is an odd integer less than 0, the
66 result is -0.
67 If x is negative infinity, and y less than 0 and not an odd integer,
69 the result is +0.
70 If x is negative infinity, and y is an odd integer greater than 0, the
72 result is negative infinity.
73 If x is negative infinity, and y greater than 0 and not an odd integer,
75 the result is positive infinity.
76 If x is positive infinity, and y less than 0, the result is +0.
78 If x is positive infinity, and y greater than 0, the result is positive
80 infinity.
81 If x is +0 or -0, and y is an odd integer less than 0, a pole error
83 occurs and HUGE_VAL, HUGE_VALF, or HUGE_VALL, is returned, with the
84 same sign as x.
85 If x is +0 or -0, and y is less than 0 and not an odd integer, a pole
87 error occurs and +HUGE_VAL, +HUGE_VALF, or +HUGE_VALL, is returned.
88
90 See math_error(7) for information on how to determine whether an error
91 has occurred when calling these functions.
92 The following errors can occur:
94 Domain error: x is negative, and y is a finite non-integer
96 errno is set to EDOM. An invalid floating-point exception
97 (FE_INVALID) is raised.
98 Pole error: x is zero, and y is negative
100 errno is set to ERANGE (but see BUGS). A divide-by-zero float‐
101 ing-point exception (FE_DIVBYZERO) is raised.
102 Range error: the result overflows
104 errno is set to ERANGE. An overflow floating-point exception
105 (FE_OVERFLOW) is raised.
106 Range error: the result underflows
108 errno is set to ERANGE. An underflow floating-point exception
109 (FE_UNDERFLOW) is raised.
110
112 C99, POSIX.1-2001. The variant returning double also conforms to SVr4,
113 4.3BSD, C89.
114
116 For a pole error, errno is set to EDOM; POSIX.1 says it should be set
117 to ERANGE.
118 If x is negative, then large negative or positive y values yield a NaN
120 as the function result, with errno set to EDOM, and an invalid
121 (FE_INVALID) floating-point exception. For example, with pow(), one
122 sees this behavior when the absolute value of y is greater than about
123 9.223373e18.
124 In version 2.3.2 and earlier, when an overflow or underflow error
126 occurs, glibc's pow() generates a bogus invalid floating-point excep‐
127 tion (FE_INVALID) in addition to the overflow or underflow exception.
128
130 cbrt(3), cpow(3), sqrt(3)
131
133 This page is part of release 3.22 of the Linux man-pages project. A
134 description of the project, and information about reporting bugs, can
135 be found at http://www.kernel.org/doc/man-pages/.
136 2008-08-10 POW(3)