man3/exp.3

   1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
   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 .\" References consulted:
   8 .\"     Linux libc source code
   9 .\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
  10 .\"     386BSD man pages
  11 .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
  12 .\" Modified 1995-08-14 by Arnt Gulbrandsen <agulbra@troll.no>
  13 .\" Modified 2002-07-27 by Walter Harms
  14 .\"     (walter.harms@informatik.uni-oldenburg.de)
  15 .\"
  16 .TH EXP 3 2022-09-09 "Linux man-pages (unreleased)"
  17 .SH NAME
  18 exp, expf, expl \- base-e exponential function
  19 .SH LIBRARY
  20 Math library
  21 .RI ( libm ", " \-lm )
  22 .SH SYNOPSIS
  23 .nf
  24 .B #include <math.h>
  25 .PP
  26 .BI "double exp(double " x );
  27 .BI "float expf(float " x );
  28 .BI "long double expl(long double " x );
  29 .fi
  30 .PP
  31 .RS -4
  32 Feature Test Macro Requirements for glibc (see
  33 .BR feature_test_macros (7)):
  34 .RE
  35 .PP
  36 .BR expf (),
  37 .BR expl ():
  38 .nf
  39     _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
  40         || /* Since glibc 2.19: */ _DEFAULT_SOURCE
  41         || /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
  42 .fi
  43 .SH DESCRIPTION
  44 These functions return the value of e (the base of natural
  45 logarithms) raised to the power of
  46 .IR x .
  47 .SH RETURN VALUE
  48 On success, these functions return the exponential value of
  49 .IR x .
  50 .PP
  51 If
  52 .I x
  53 is a NaN,
  54 a NaN is returned.
  55 .PP
  56 If
  57 .I x
  58 is positive infinity,
  59 positive infinity is returned.
  60 .PP
  61 If
  62 .I x
  63 is negative infinity,
  64 +0 is returned.
  65 .PP
  66 If the result underflows,
  67 a range error occurs,
  68 and zero is returned.
  69 .PP
  70 If the result overflows,
  71 a range error occurs,
  72 and the functions return
  73 .RB + HUGE_VAL ,
  74 .RB + HUGE_VALF ,
  75 or
  76 .RB + HUGE_VALL ,
  77 respectively.
  78 .SH ERRORS
  79 See
  80 .BR math_error (7)
  81 for information on how to determine whether an error has occurred
  82 when calling these functions.
  83 .PP
  84 The following errors can occur:
  85 .TP
  86 Range error, overflow
  87 .I errno
  88 is set to
  89 .BR ERANGE .
  90 An overflow floating-point exception
  91 .RB ( FE_OVERFLOW )
  92 is raised.
  93 .TP
  94 Range error, underflow
  95 .I errno
  96 is set to
  97 .BR ERANGE .
  98 An underflow floating-point exception
  99 .RB ( FE_UNDERFLOW )
 100 is raised.
 101 .SH ATTRIBUTES
 102 For an explanation of the terms used in this section, see
 103 .BR attributes (7).
 104 .ad l
 105 .nh
 106 .TS
 107 allbox;
 108 lbx lb lb
 109 l l l.
 110 Interface       Attribute       Value
 111 T{
 112 .BR exp (),
 113 .BR expf (),
 114 .BR expl ()
 115 T}      Thread safety   MT-Safe
 116 .TE
 117 .hy
 118 .ad
 119 .sp 1
 120 .SH STANDARDS
 121 C99, POSIX.1-2001, POSIX.1-2008.
 122 .PP
 123 The variant returning
 124 .I double
 125 also conforms to
 126 SVr4, 4.3BSD, C89.
 127 .SH SEE ALSO
 128 .BR cbrt (3),
 129 .BR cexp (3),
 130 .BR exp10 (3),
 131 .BR exp2 (3),
 132 .BR expm1 (3),
 133 .BR sqrt (3)