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32.\" from: @(#)exp.3 6.12 (Berkeley) 7/31/91
33.\" $Id: pow.3,v 1.4 2004/12/20 21:35:46 scp Exp $
34.\"
35.Dd December 11, 2006
36.Dt POW 3
37.Os BSD 4
38.Sh NAME
39.Nm pow
40.Nd power function
41.Sh SYNOPSIS
42.Fd #include <math.h>
43.Ft double
44.Fn pow "double x" "double y"
45.Ft long double
46.Fn powl "long double x" "long double y"
47.Ft float
48.Fn powf "float x" "float y"
49.Sh DESCRIPTION
50The
51.Fn pow
52functions compute
53.Fa x
54raised to the power
55.Fa y .
56.Sh SPECIAL VALUES
57.Fn pow "�0" "y"
58returns �infinity and raises the "divide-by-zero" floating-point exception for y an odd integer < 0.
59.Pp
60.Fn pow "�0" "y"
61returns +infinity and raises the "divide-by-zero" floating-point exception for y < 0 and not an odd integer.
62.Pp
63.Fn pow "�0" "y"
64returns �0 for y an odd integer > 0.
65.Pp
66.Fn pow "�0" "y"
67returns +0 for y > 0 and not an odd integer.
68.Pp
69.Fn pow "-1" "�infinity"
70returns 1.
71.Pp
72.Fn pow "1" "y"
73returns 1 for any y, even a NaN.
74.Pp
75.Fn pow "x" "�0"
76returns 1 for any x, even a NaN.
77.Pp
78.Fn pow "x" "y"
79returns a NaN and raises the "invalid" floating-point exception for finite x < 0 and finite non-integer y.
80.Pp
81.Fn pow "x" "-infinity"
82returns +infinity for |x| < 1.
83.Pp
84.Fn pow "x" "-infinity"
85returns +0 for |x| > 1.
86.Pp
87.Fn pow "x" "+infinity"
88returns +0 for |x| < 1.
89.Pp
90.Fn pow "x" "+infinity"
91returns +infinity for |x| > 1.
92.Pp
93.Fn pow "-infinity" "y"
94returns -0 for y an odd integer < 0.
95.Pp
96.Fn pow "-infinity" "y"
97returns +0 for y < 0 and not an odd integer.
98.Pp
99.Fn pow "-infinity" "y"
100returns -infinity for y an odd integer > 0.
101.Pp
102.Fn pow "-infinity" "y"
103returns +infinity for y > 0 and not an odd integer.
104.Pp
105.Fn pow "+infinity" "y"
106returns +0 for y < 0.
107.Pp
108.Fn pow "+infinity" "y"
109returns +infinity for y > 0.
110.Pp
111A domain error occurs if x is finite and negative and y is finite and not an integer.
112.Pp
113A domain error can occur if x is 0 and y less than or equal to 0.
114.Pp
115Range errors may occur.
116.Sh SEE ALSO
117.Xr math 3
118.Sh STANDARDS
119The
120.Fn pow
121function conforms to ISO/IEC 9899:1999(E).