man3/scalb.3

   1 .\" Copyright 2004 Andries Brouwer <aeb@cwi.nl>.
   2 .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
   3 .\"     <mtk.manpages@gmail.com>
   4 .\"
   5 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
   6 .\"
   7 .TH SCALB 3 2021-03-22 GNU "Linux Programmer's Manual"
   8 .SH NAME
   9 scalb, scalbf, scalbl \- multiply floating-point number
  10 by integral power of radix (OBSOLETE)
  11 .SH LIBRARY
  12 Math library
  13 .RI ( libm ", " \-lm )
  14 .SH SYNOPSIS
  15 .nf
  16 .B #include <math.h>
  17 .PP
  18 .BI "double scalb(double " x ", double " exp );
  19 .BI "float scalbf(float " x ", float " exp );
  20 .BI "long double scalbl(long double " x ", long double " exp );
  21 .fi
  22 .PP
  23 .RS -4
  24 Feature Test Macro Requirements for glibc (see
  25 .BR feature_test_macros (7)):
  26 .RE
  27 .PP
  28 .BR scalb ():
  29 .nf
  30     _XOPEN_SOURCE >= 500
  31 .\"    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
  32         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  33         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  34 .fi
  35 .PP
  36 .BR scalbf (),
  37 .BR scalbl ():
  38 .nf
  39     _XOPEN_SOURCE >= 600
  40         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  41         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  42 .fi
  43 .SH DESCRIPTION
  44 These functions multiply their first argument
  45 .I x
  46 by
  47 .B FLT_RADIX
  48 (probably 2)
  49 to the power of
  50 .IR exp ,
  51 that is:
  52 .PP
  53 .nf
  54     x * FLT_RADIX ** exp
  55 .fi
  56 .PP
  57 The definition of
  58 .B FLT_RADIX
  59 can be obtained by including
  60 .IR <float.h> .
  61 .\" not in /usr/include but in a gcc lib
  62 .SH RETURN VALUE
  63 On success, these functions return
  64 .I x
  65 *
  66 .B FLT_RADIX
  67 **
  68 .IR exp .
  69 .PP
  70 If
  71 .I x
  72 or
  73 .I exp
  74 is a NaN, a NaN is returned.
  75 .PP
  76 If
  77 .I x
  78 is positive infinity (negative infinity),
  79 and
  80 .I exp
  81 is not negative infinity,
  82 positive infinity (negative infinity) is returned.
  83 .PP
  84 If
  85 .I x
  86 is +0 (\-0), and
  87 .I exp
  88 is not positive infinity, +0 (\-0) is returned.
  89 .PP
  90 If
  91 .I x
  92 is zero, and
  93 .I exp
  94 is positive infinity,
  95 a domain error occurs, and
  96 a NaN is returned.
  97 .PP
  98 If
  99 .I x
 100 is an infinity,
 101 and
 102 .I exp
 103 is negative infinity,
 104 a domain error occurs, and
 105 a NaN is returned.
 106 .PP
 107 If the result overflows,
 108 a range error occurs,
 109 and the functions return
 110 .BR HUGE_VAL ,
 111 .BR HUGE_VALF ,
 112 or
 113 .BR HUGE_VALL ,
 114 respectively, with a sign the same as
 115 .IR x .
 116 .PP
 117 If the result underflows,
 118 a range error occurs,
 119 and the functions return zero, with a sign the same as
 120 .IR x .
 121 .SH ERRORS
 122 See
 123 .BR math_error (7)
 124 for information on how to determine whether an error has occurred
 125 when calling these functions.
 126 .PP
 127 The following errors can occur:
 128 .TP
 129 Domain error: \fIx\fP is 0, and \fIexp\fP is positive infinity, \
 130 or \fIx\fP is positive infinity and \fIexp\fP is negative infinity \
 131 and the other argument is not a NaN
 132 .I errno
 133 is set to
 134 .BR EDOM .
 135 An invalid floating-point exception
 136 .RB ( FE_INVALID )
 137 is raised.
 138 .TP
 139 Range error, overflow
 140 .I errno
 141 is set to
 142 .BR ERANGE .
 143 An overflow floating-point exception
 144 .RB ( FE_OVERFLOW )
 145 is raised.
 146 .TP
 147 Range error, underflow
 148 .I errno
 149 is set to
 150 .BR ERANGE .
 151 An underflow floating-point exception
 152 .RB ( FE_UNDERFLOW )
 153 is raised.
 154 .SH ATTRIBUTES
 155 For an explanation of the terms used in this section, see
 156 .BR attributes (7).
 157 .ad l
 158 .nh
 159 .TS
 160 allbox;
 161 lbx lb lb
 162 l l l.
 163 Interface       Attribute       Value
 164 T{
 165 .BR scalb (),
 166 .BR scalbf (),
 167 .BR scalbl ()
 168 T}      Thread safety   MT-Safe
 169 .TE
 170 .hy
 171 .ad
 172 .sp 1
 173 .SH CONFORMING TO
 174 .BR scalb ()
 175 is specified in POSIX.1-2001, but marked obsolescent.
 176 POSIX.1-2008 removes the specification of
 177 .BR scalb (),
 178 recommending the use of
 179 .BR scalbln (3),
 180 .BR scalblnf (3),
 181 or
 182 .BR scalblnl (3)
 183 instead.
 184 The
 185 .BR scalb ()
 186 function is from 4.3BSD.
 187 .PP
 188 .BR scalbf ()
 189 and
 190 .BR scalbl ()
 191 are unstandardized;
 192 .BR scalbf ()
 193 is nevertheless present on several other systems
 194 .\" Looking at header files: scalbf() is present on the
 195 .\" BSDs, Tru64, HP-UX 11, Irix 6.5; scalbl() is on HP-UX 11 and Tru64.
 196 .SH BUGS
 197 Before glibc 2.20,
 198 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803
 199 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=6804
 200 these functions did not set
 201 .I errno
 202 for domain and range errors.
 203 .SH SEE ALSO
 204 .BR ldexp (3),
 205 .BR scalbln (3)