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  12 .TH expm1 3M "12 Jul 2006" "SunOS 5.11" "Mathematical Library Functions"
  13 .SH NAME
  14 expm1, expm1f, expm1l \- compute exponential function
  15 .SH SYNOPSIS
  16 .LP
  17 .nf
  18 c99 [ \fIflag\fR... ] \fIfile\fR... \fB-lm\fR [ \fIlibrary\fR... ]
  19 #include <math.h>
  20 
  21 \fBdouble\fR \fBexpm1\fR(\fBdouble\fR \fIx\fR);
  22 .fi
  23 
  24 .LP
  25 .nf
  26 \fBfloat\fR \fBexpm1f\fR(\fBfloat\fR \fIx\fR);
  27 .fi
  28 
  29 .LP
  30 .nf
  31 \fBlong double\fR \fBexpm1l\fR(\fBlong double\fR \fIx\fR);
  32 .fi
  33 
  34 .SH DESCRIPTION
  35 .sp
  36 .LP
  37 These functions compute \fIe\fR^\fIx\fR\(mi1.0.
  38 .SH RETURN VALUES
  39 .sp
  40 .LP
  41 Upon successful completion, these functions return \fIe\fR^\fIx\fR\(mi1.0.
  42 .sp
  43 .LP
  44 If \fIx\fR is NaN, a NaN is returned.
  45 .sp
  46 .LP
  47 If \fIx\fR is \(+-0, \(+-0 is returned.
  48 .sp
  49 .LP
  50 If \fIx\fR is \(miInf, \(mi1 is returned.
  51 .sp
  52 .LP
  53 If \fIx\fR is +Inf, \fIx\fR is returned.
  54 .SH ERRORS
  55 .sp
  56 .LP
  57 These functions will fail if:
  58 .sp
  59 .ne 2
  60 .mk
  61 .na
  62 \fBRange Error\fR
  63 .ad
  64 .RS 15n
  65 .rt  
  66 The result overflows.
  67 .sp
  68 If the integer expression (\fBmath_errhandling\fR & \fBMATH_ERREXCEPT\fR) is
  69 non-zero, the overflow floating-point exception is raised.
  70 .RE
  71 
  72 .SH USAGE
  73 .sp
  74 .LP
  75 The value of \fBexpm1(\fR\fIx\fR\fB)\fR can be more accurate than
  76 \fBexp(\fIx\fR)\fR\(mi1.0 for small values of \fIx\fR.
  77 .sp
  78 .LP
  79 The \fBexpm1()\fR and \fBlog1p\fR(3M) functions are useful for financial
  80 calculations of ((1+\fIx\fR)^\fIn\fR\(mi1)/\fIx\fR, namely:
  81 .sp
  82 .in +2
  83 .nf
  84 \fBexpm1(\fIn\fR * log1p(\fIx\fR))\|/\|\fR\fIx\fR
  85 .fi
  86 .in -2
  87 
  88 .sp
  89 .LP
  90 when \fIx\fR is very small (for example, when performing calculations with a
  91 small daily interest rate).  These functions also simplify writing accurate
  92 inverse hyperbolic functions.
  93 .sp
  94 .LP
  95 An application wanting to check for exceptions should call
  96 \fBfeclearexcept\fR(\fBFE_ALL_EXCEPT\fR) before calling these functions. On
  97 return, if \fBfetestexcept\fR(\fBFE_INVALID\fR | \fBFE_DIVBYZERO\fR |
  98 \fBFE_OVERFLOW\fR | \fBFE_UNDERFLOW\fR) is non-zero, an exception has been
  99 raised. An application should either examine the return value or check the
 100 floating point exception flags to detect exceptions.
 101 .SH ATTRIBUTES
 102 .sp
 103 .LP
 104 See \fBattributes\fR(5) for descriptions of the following attributes:
 105 .sp
 106 
 107 .sp
 108 .TS
 109 tab() box;
 110 cw(2.75i) |cw(2.75i) 
 111 lw(2.75i) |lw(2.75i) 
 112 .
 113 ATTRIBUTE TYPEATTRIBUTE VALUE
 114 _
 115 Interface StabilityStandard
 116 _
 117 MT-LevelMT-Safe
 118 .TE
 119 
 120 .SH SEE ALSO
 121 .sp
 122 .LP
 123 \fBexp\fR(3M), \fBfeclearexcept\fR(3M), \fBfetestexcept\fR(3M),
 124 \fBilogb\fR(3M), \fBlog1p\fR(3M), \fBmath.h\fR(3HEAD), \fBattributes\fR(5),
 125 \fBstandards\fR(5)