xref: /minix3/lib/libm/man/log.3 (revision 84d9c625bfea59e274550651111ae9edfdc40fbd)
1*84d9c625SLionel Sambuc.\" $NetBSD: log.3,v 1.3 2011/09/13 08:51:32 wiz Exp $
2*84d9c625SLionel Sambuc.\"
3*84d9c625SLionel Sambuc.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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5*84d9c625SLionel Sambuc.\"
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7*84d9c625SLionel Sambuc.\" modification, are permitted provided that the following conditions
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27*84d9c625SLionel Sambuc.Dd September 13, 2011
28*84d9c625SLionel Sambuc.Dt LOG 3
29*84d9c625SLionel Sambuc.Os
30*84d9c625SLionel Sambuc.Sh NAME
31*84d9c625SLionel Sambuc.Nm log ,
32*84d9c625SLionel Sambuc.Nm logf ,
33*84d9c625SLionel Sambuc.Nm log10 ,
34*84d9c625SLionel Sambuc.Nm log10f ,
35*84d9c625SLionel Sambuc.Nm log1p ,
36*84d9c625SLionel Sambuc.Nm log1pf
37*84d9c625SLionel Sambuc.Nm log2 ,
38*84d9c625SLionel Sambuc.Nm log2f ,
39*84d9c625SLionel Sambuc.Nd logarithm functions
40*84d9c625SLionel Sambuc.Sh LIBRARY
41*84d9c625SLionel Sambuc.Lb libm
42*84d9c625SLionel Sambuc.Sh SYNOPSIS
43*84d9c625SLionel Sambuc.In math.h
44*84d9c625SLionel Sambuc.Ft double
45*84d9c625SLionel Sambuc.Fn log "double x"
46*84d9c625SLionel Sambuc.Ft float
47*84d9c625SLionel Sambuc.Fn logf "float x"
48*84d9c625SLionel Sambuc.Ft double
49*84d9c625SLionel Sambuc.Fn log10 "double x"
50*84d9c625SLionel Sambuc.Ft float
51*84d9c625SLionel Sambuc.Fn log10f "float x"
52*84d9c625SLionel Sambuc.Ft double
53*84d9c625SLionel Sambuc.Fn log1p "double x"
54*84d9c625SLionel Sambuc.Ft float
55*84d9c625SLionel Sambuc.Fn log1pf "float x"
56*84d9c625SLionel Sambuc.Ft double
57*84d9c625SLionel Sambuc.Fn log2 "double x"
58*84d9c625SLionel Sambuc.Ft float
59*84d9c625SLionel Sambuc.Fn log2f "float x"
60*84d9c625SLionel Sambuc.Sh DESCRIPTION
61*84d9c625SLionel SambucThe following functions compute logarithms:
62*84d9c625SLionel Sambuc.Bl -bullet -offset 2n
63*84d9c625SLionel Sambuc.It
64*84d9c625SLionel SambucThe
65*84d9c625SLionel Sambuc.Fn log
66*84d9c625SLionel Sambucand
67*84d9c625SLionel Sambuc.Fn logf
68*84d9c625SLionel Sambucfunctions return the natural logarithm.
69*84d9c625SLionel Sambuc.It
70*84d9c625SLionel SambucThe
71*84d9c625SLionel Sambuc.Fn log10
72*84d9c625SLionel Sambucand
73*84d9c625SLionel Sambuc.Fn log10f
74*84d9c625SLionel Sambucfunctions return the base 10 logarithm.
75*84d9c625SLionel Sambuc.It
76*84d9c625SLionel SambucThe
77*84d9c625SLionel Sambuc.Fn log1p
78*84d9c625SLionel Sambucand
79*84d9c625SLionel Sambuc.Fn log1pf
80*84d9c625SLionel Sambucfunctions return the natural logarithm of (1.0 +
81*84d9c625SLionel Sambuc.Fa x )
82*84d9c625SLionel Sambucaccurately even for very small values of
83*84d9c625SLionel Sambuc.Fa x .
84*84d9c625SLionel Sambuc.It
85*84d9c625SLionel SambucThe
86*84d9c625SLionel Sambuc.Fn log2
87*84d9c625SLionel Sambucand
88*84d9c625SLionel Sambuc.Fn log2f
89*84d9c625SLionel Sambucfunctions return the base 2 logarithm.
90*84d9c625SLionel Sambuc.El
91*84d9c625SLionel Sambuc.Sh RETURN VALUES
92*84d9c625SLionel SambucUpon successful completion, the functions return the logarithm of
93*84d9c625SLionel Sambuc.Fa x
94*84d9c625SLionel Sambucas descibed above.
95*84d9c625SLionel SambucOtherwise the following may occur:
96*84d9c625SLionel Sambuc.Bl -enum -offset indent
97*84d9c625SLionel Sambuc.It
98*84d9c625SLionel SambucIf
99*84d9c625SLionel Sambuc.Fa x
100*84d9c625SLionel Sambucis \*(Na, all functions return \*(Na.
101*84d9c625SLionel Sambuc.It
102*84d9c625SLionel SambucIf
103*84d9c625SLionel Sambuc.Fa x
104*84d9c625SLionel Sambucis positive infinity, all functions return
105*84d9c625SLionel Sambuc.Fa x .
106*84d9c625SLionel SambucIf
107*84d9c625SLionel Sambuc.Fa x
108*84d9c625SLionel Sambucis negative infinity, all functions return \*(Na.
109*84d9c625SLionel Sambuc.It
110*84d9c625SLionel SambucIf
111*84d9c625SLionel Sambuc.Fa x
112*84d9c625SLionel Sambucis +0.0 or -0.0, the
113*84d9c625SLionel Sambuc.Fn log ,
114*84d9c625SLionel Sambuc.Fn log10 ,
115*84d9c625SLionel Sambucand
116*84d9c625SLionel Sambuc.Fn log2
117*84d9c625SLionel Sambucfamilies return either
118*84d9c625SLionel Sambuc.Dv -HUGE_VAL ,
119*84d9c625SLionel Sambuc.Dv -HUGE_VALF ,
120*84d9c625SLionel Sambucor
121*84d9c625SLionel Sambuc.Dv -HUGE_VALL ,
122*84d9c625SLionel Sambucwhereas the
123*84d9c625SLionel Sambuc.Fn log1p
124*84d9c625SLionel Sambucfamily returns
125*84d9c625SLionel Sambuc.Fa x .
126*84d9c625SLionel Sambuc.It
127*84d9c625SLionel SambucIf
128*84d9c625SLionel Sambuc.Fa x
129*84d9c625SLionel Sambucis +1.0, the
130*84d9c625SLionel Sambuc.Fn log ,
131*84d9c625SLionel Sambuc.Fn log10 ,
132*84d9c625SLionel Sambucand
133*84d9c625SLionel Sambuc.Fn log2
134*84d9c625SLionel Sambucfamilies return +0.0.
135*84d9c625SLionel SambucIf
136*84d9c625SLionel Sambuc.Fa x
137*84d9c625SLionel Sambucis -1.0, the
138*84d9c625SLionel Sambuc.Fn log1p
139*84d9c625SLionel Sambucfamily returns
140*84d9c625SLionel Sambuc.Dv -HUGE_VAL ,
141*84d9c625SLionel Sambuc.Dv -HUGE_VALF ,
142*84d9c625SLionel Sambucor
143*84d9c625SLionel Sambuc.Dv -HUGE_VALL .
144*84d9c625SLionel Sambuc.El
145*84d9c625SLionel Sambuc.Pp
146*84d9c625SLionel SambucIn addition, on a
147*84d9c625SLionel Sambuc.Tn VAX ,
148*84d9c625SLionel Sambuc.Va errno
149*84d9c625SLionel Sambucis set to
150*84d9c625SLionel Sambuc.Er EDOM
151*84d9c625SLionel Sambucand the reserved operand is returned
152*84d9c625SLionel Sambucby
153*84d9c625SLionel Sambuc.Fn log
154*84d9c625SLionel Sambucunless
155*84d9c625SLionel Sambuc.Fa x
156*84d9c625SLionel Sambuc\*[Gt] 0, by
157*84d9c625SLionel Sambuc.Fn log1p
158*84d9c625SLionel Sambucunless
159*84d9c625SLionel Sambuc.Fa x
160*84d9c625SLionel Sambuc\*[Gt] \-1.
161*84d9c625SLionel Sambuc.Sh SEE ALSO
162*84d9c625SLionel Sambuc.Xr exp 3 ,
163*84d9c625SLionel Sambuc.Xr ilogb 3 ,
164*84d9c625SLionel Sambuc.Xr math 3
165*84d9c625SLionel Sambuc.Sh STANDARDS
166*84d9c625SLionel SambucThe described functions conform to
167*84d9c625SLionel Sambuc.St -isoC-99 .
168*84d9c625SLionel Sambuc.Sh HISTORY
169*84d9c625SLionel SambucThe history of the logarithm functions dates back to
170*84d9c625SLionel Sambuc.At v6 .
171