man3/scalbln.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 SCALBLN 3 2008-08-11 "" "Linux Programmer's Manual"
  26 .SH NAME
  27 scalbn, scalbnf, scalbnl, scalbln, scalblnf, scalblnl \-
  28 multiply floating-point number by integral power of radix
  29 .SH SYNOPSIS
  30 .B #include <math.h>
  31 .sp
  32 .BI "double scalbln(double " x ", long int " exp );
  33 .br
  34 .BI "float scalblnf(float " x ", long int " exp );
  35 .br
  36 .BI "long double scalblnl(long double " x ", long int " exp );
  37 .sp
  38 .BI "double scalbn(double " x ", int " exp );
  39 .br
  40 .BI "float scalbnf(float " x ", int " exp );
  41 .br
  42 .BI "long double scalbnl(long double " x ", int " exp );
  43 .sp
  44 Link with \fI\-lm\fP.
  45 .sp
  46 .in -4n
  47 Feature Test Macro Requirements for glibc (see
  48 .BR feature_test_macros (7)):
  49 .in
  50 .sp
  51 .ad l
  52 .BR scalbln (),
  53 .BR scalblnf (),
  54 .BR scalblnl ():
  55 .RS
  56 _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
  57 _POSIX_C_SOURCE\ >=\ 200112L;
  58 .br
  59 or
  60 .I cc\ -std=c99
  61 .RE
  62 .br
  63 .BR scalbn (),
  64 .BR scalbnf (),
  65 .BR scalbnl ():
  66 .RS
  67 _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
  68 _POSIX_C_SOURCE\ >=\ 200112L;
  69 .br
  70 or
  71 .I cc\ -std=c99
  72 .RE
  73 .ad b
  74 .SH DESCRIPTION
  75 These functions multiply their first argument
  76 .I x
  77 by
  78 .B FLT_RADIX
  79 (probably 2)
  80 to the power of
  81 .IR exp ,
  82 that is:
  83 .nf
  84
  85     x * FLT_RADIX ** exp
  86 .fi
  87
  88 The definition of
  89 .B FLT_RADIX
  90 can be obtained by including
  91 .IR <float.h> .
  92 .\" not in /usr/include but in a gcc lib
  93 .SH RETURN VALUE
  94 On success, these functions return \fIx\fP * \fBFLT_RADIX\fP ** \fIexp\fP.
  95
  96 If
  97 .I x
  98 is a NaN, a NaN is returned.
  99
 100 If
 101 .I x
 102 is positive infinity (negative infinity),
 103 positive infinity (negative infinity) is returned.
 104
 105 If
 106 .I x
 107 is +0 (\-0), +0 (\-0) is returned.
 108
 109 If the result overflows,
 110 a range error occurs,
 111 and the functions return
 112 .BR HUGE_VAL ,
 113 .BR HUGE_VALF ,
 114 or
 115 .BR HUGE_VALL ,
 116 respectively, with a sign the same as
 117 .IR x .
 118
 119 If the result underflows,
 120 a range error occurs,
 121 and the functions return zero, with a sign the same as
 122 .IR x .
 123 .SH ERRORS
 124 See
 125 .BR math_error (7)
 126 for information on how to determine whether an error has occurred
 127 when calling these functions.
 128 .PP
 129 The following errors can occur:
 130 .TP
 131 Range error, overflow
 132 .\" .I errno
 133 .\" is set to
 134 .\" .BR ERANGE .
 135 An overflow floating-point exception
 136 .RB ( FE_OVERFLOW )
 137 is raised.
 138 .TP
 139 Range error, underflow
 140 .\" .I errno
 141 .\" is set to
 142 .\" .BR ERANGE .
 143 An underflow floating-point exception
 144 .RB ( FE_UNDERFLOW )
 145 is raised.
 146 .PP
 147 These functions do not set
 148 .IR errno .
 149 .\" FIXME . Is it intentional that these functions do not set errno?
 150 .\" Bug raised: http://sources.redhat.com/bugzilla/show_bug.cgi?id=6803
 151 .SH VERSIONS
 152 These functions first appeared in glibc in version 2.1.
 153 .SH "CONFORMING TO"
 154 C99, POSIX.1-2001.
 155 .SH NOTES
 156 These functions differ from the obsolete functions described in
 157 .BR scalb (3)
 158 in the type of their second argument.
 159 The functions described on this page have a second argument
 160 of an integral type, while those in
 161 .BR scalb (3)
 162 have a second argument of type
 163 .IR double .
 164
 165 If
 166 .B FLT_RADIX
 167 equals 2 (which is usual), then
 168 .BR scalbn ()
 169 is equivalent to
 170 .BR ldexp (3).
 171 .SH "SEE ALSO"
 172 .BR ldexp (3),
 173 .BR scalb (3)