man3/scalb.3

   1 .\" Copyright 2004 Andries Brouwer <aeb@cwi.nl>.
   2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
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  27 .TH SCALB 3 2015-03-02 "" "Linux Programmer's Manual"
  28 .SH NAME
  29 scalb, scalbf, scalbl \- multiply floating-point number
  30 by integral power of radix (OBSOLETE)
  31 .SH SYNOPSIS
  32 .B #include <math.h>
  33 .sp
  34 .BI "double scalb(double " x ", double " exp );
  35 .br
  36 .BI "float scalbf(float " x ", float " exp );
  37 .br
  38 .BI "long double scalbl(long double " x ", long double " exp );
  39 .sp
  40 Link with \fI\-lm\fP.
  41 .sp
  42 .in -4n
  43 Feature Test Macro Requirements for glibc (see
  44 .BR feature_test_macros (7)):
  45 .in
  46 .sp
  47 .ad l
  48 .BR scalb ():
  49 .RS 4
  50 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
  51 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
  52 .RE
  53 .br
  54 .BR scalbf (),
  55 .BR scalbl ():
  56 .RS 4
  57 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600
  58 .RE
  59 .ad b
  60 .SH DESCRIPTION
  61 These functions multiply their first argument
  62 .I x
  63 by
  64 .B FLT_RADIX
  65 (probably 2)
  66 to the power of
  67 .IR exp ,
  68 that is:
  69 .nf
  70
  71     x * FLT_RADIX ** exp
  72 .fi
  73
  74 The definition of
  75 .B FLT_RADIX
  76 can be obtained by including
  77 .IR <float.h> .
  78 .\" not in /usr/include but in a gcc lib
  79 .SH RETURN VALUE
  80 On success, these functions return
  81 .IR x
  82 *
  83 .B FLT_RADIX
  84 **
  85 .IR exp .
  86
  87 If
  88 .I x
  89 or
  90 .I exp
  91 is a NaN, a NaN is returned.
  92
  93 If
  94 .I x
  95 is positive infinity (negative infinity),
  96 and
  97 .I exp
  98 is not negative infinity,
  99 positive infinity (negative infinity) is returned.
 100
 101 If
 102 .I x
 103 is +0 (\-0), and
 104 .I exp
 105 is not positive infinity, +0 (\-0) is returned.
 106
 107 If
 108 .I x
 109 is zero, and
 110 .I exp
 111 is positive infinity,
 112 a domain error occurs, and
 113 a NaN is returned.
 114
 115 If
 116 .I x
 117 is an infinity,
 118 and
 119 .I exp
 120 is negative infinity,
 121 a domain error occurs, and
 122 a NaN is returned.
 123
 124 If the result overflows,
 125 a range error occurs,
 126 and the functions return
 127 .BR HUGE_VAL ,
 128 .BR HUGE_VALF ,
 129 or
 130 .BR HUGE_VALL ,
 131 respectively, with a sign the same as
 132 .IR x .
 133
 134 If the result underflows,
 135 a range error occurs,
 136 and the functions return zero, with a sign the same as
 137 .IR x .
 138 .SH ERRORS
 139 See
 140 .BR math_error (7)
 141 for information on how to determine whether an error has occurred
 142 when calling these functions.
 143 .PP
 144 The following errors can occur:
 145 .TP
 146 Domain error: \fIx\fP is 0, and \fIexp\fP is positive infinity, \
 147 or \fIx\fP is positive infinity and \fIexp\fP is negative infinity \
 148 and the other argument is not a NaN
 149 .\" .I errno
 150 .\" is set to
 151 .\" .BR EDOM .
 152 An invalid floating-point exception
 153 .RB ( FE_INVALID )
 154 is raised.
 155 .TP
 156 Range error, overflow
 157 .\" .I errno
 158 .\" is set to
 159 .\" .BR ERANGE .
 160 An overflow floating-point exception
 161 .RB ( FE_OVERFLOW )
 162 is raised.
 163 .TP
 164 Range error, underflow
 165 .\" .I errno
 166 .\" is set to
 167 .\" .BR ERANGE .
 168 An underflow floating-point exception
 169 .RB ( FE_UNDERFLOW )
 170 is raised.
 171 .PP
 172 These functions do not set
 173 .IR errno .
 174 .\" FIXME . Is it intentional that these functions do not set errno?
 175 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803
 176 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6804
 177 .SH ATTRIBUTES
 178 For an explanation of the terms used in this section, see
 179 .BR attributes (7).
 180 .TS
 181 allbox;
 182 lbw28 lb lb
 183 l l l.
 184 Interface       Attribute       Value
 185 T{
 186 .BR scalb (),
 187 .BR scalbf (),
 188 .BR scalbl ()
 189 T}      Thread safety   MT-Safe
 190 .TE
 191 .SH CONFORMING TO
 192 .BR scalb ()
 193 is specified in POSIX.1-2001, but marked obsolescent.
 194 POSIX.1-2008 removes the specification of
 195 .BR scalb (),
 196 recommending the use of
 197 .BR scalbln (3),
 198 .BR scalblnf (3),
 199 or
 200 .BR scalblnl (3)
 201 instead.
 202 The
 203 .BR scalb ()
 204 function is from 4.3BSD.
 205
 206 .BR scalbf ()
 207 and
 208 .BR scalbl ()
 209 are unstandardized;
 210 .BR scalbf ()
 211 is nevertheless present on several other systems
 212 .\" Looking at header files: scalbf() is present on the
 213 .\" BSDs, Tru64, HP-UX 11, Irix 6.5; scalbl() is on HP-UX 11 and Tru64.
 214 .SH SEE ALSO
 215 .BR ldexp (3),
 216 .BR scalbln (3)