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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  25 .TH SCALB 3 2008-07-29 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 scalb, scalbf, scalbl \- multiply floating-point number
  28 by integral power of radix (OBSOLETE)
  29 .SH SYNOPSIS
  30 .B #include <math.h>
  31 .sp
  32 .BI "double scalb(double " x ", double " exp );
  33 .br
  34 .BI "float scalbf(float " x ", double " exp );
  35 .br
  36 .BI "long double scalbl(long double " x ", double " exp );
  37 .sp
  38 Link with \fI\-lm\fP.
  39 .sp
  40 .in -4n
  41 Feature Test Macro Requirements for glibc (see
  42 .BR feature_test_macros (7)):
  43 .in
  44 .sp
  45 .ad l
  46 .BR scalb ():
  47 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 500
  48 .br
  49 .BR scalbf (),
  50 .BR scalbl ():
  51 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600
  52 .ad b
  53 .SH DESCRIPTION
  54 These functions multiply their first argument
  55 .I x
  56 by
  57 .B FLT_RADIX
  58 (probably 2)
  59 to the power of
  60 .IR exp ,
  61 that is:
  62 .nf
  63
  64     x * FLT_RADIX ** exp
  65 .fi
  66
  67 The definition of
  68 .B FLT_RADIX
  69 can be obtained by including
  70 .IR <float.h> .
  71 .\" not in /usr/include but in a gcc lib
  72 .SH RETURN VALUE
  73 On success, these functions return \fIx\fP * \fBFLT_RADIX\fP ** \fIexp\fP.
  74
  75 If
  76 .I x
  77 or
  78 .I exp
  79 is a NaN, a NaN is returned.
  80
  81 If
  82 .I x
  83 is positive infinity (negative infinity),
  84 and
  85 .I exp
  86 is not negative infinity,
  87 positive infinity (negative infinity) is returned.
  88
  89 If
  90 .I x
  91 is +0 (\-0), and
  92 .I exp
  93 is not positive infinity, +0 (\-0) is returned.
  94
  95 If
  96 .I x
  97 is zero, and
  98 .I exp
  99 is positive infinity,
 100 a "domain error" occurs, and
 101 a NaN is returned.
 102
 103 If
 104 .I x
 105 is an infinity,
 106 and
 107 .I exp
 108 is negative infinity,
 109 a "domain error" occurs, and
 110 a NaN is returned.
 111
 112 If the result overflows,
 113 a "range error" occurs,
 114 and the functions return
 115 .BR HUGE_VAL ,
 116 .BR HUGE_VALF ,
 117 or
 118 .BR HUGE_VALL ,
 119 respectively, with a sign the same as
 120 .IR x .
 121
 122 If the result underflows,
 123 a "range error" occurs,
 124 and the functions return zero, with a sign the same as
 125 .IR x .
 126 .SH ERRORS
 127 See
 128 .BR math_error (7)
 129 for information on how to determine whether an error has occurred
 130 when calling these functions.
 131 .PP
 132 The following errors can occur:
 133 .TP
 134 Domain error: \fIx\fP is 0, and \fIexp\fP is positive infinity, \
 135 or \fIx\fP is positive infinity and \fIexp\fP is negative infinity
 136 and the other argument is not a NaN
 137 .\" .I errno
 138 .\" is set to
 139 .\" .BR EDOM .
 140 An invalid floating-point exception
 141 .RB ( FE_INVALID )
 142 is raised.
 143 .TP
 144 Range error, overflow
 145 .\" .I errno
 146 .\" is set to
 147 .\" .BR ERANGE .
 148 An overflow floating-point exception
 149 .RB ( FE_OVERFLOW )
 150 is raised.
 151 .TP
 152 Range error, underflow
 153 .\" .I errno
 154 .\" is set to
 155 .\" .BR ERANGE .
 156 An underflow floating-point exception
 157 .RB ( FE_UNDERFLOW )
 158 is raised.
 159 .PP
 160 These functions do not set
 161 .IR errno .
 162 .\" FIXME . Is it intentional that these functions do not set errno?
 163 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803
 164 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6804
 165 .SH "CONFORMING TO"
 166 .BR scalb ()
 167 is specified in POSIX.1-2001, but marked obsolescent.
 168 .\" FIXME . Mar 08: The next POSIX.1 revision removes scalb().
 169 The
 170 .BR scalb ()
 171 function is from 4.3BSD.
 172
 173 .BR scalbf ()
 174 and
 175 .BR scalbl ()
 176 are unstandardized;
 177 .BR scalbf ()
 178 is nevertheless present on several other systems
 179 .\" Looking at header files: scalbf() is present on the
 180 .\" BSDs, Tru64, HP-UX 11, Irix 6.5; scalbl() is on HP-UX 11 and Tru64.
 181 .SH "SEE ALSO"
 182 .BR ldexp (3),
 183 .BR scalbln (3)