HP-UX Reference (11i v1 00/12) - 3 Library Functions A-M (vol 6)

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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
/build/1111/BRICK/man3/!!!intro.3c
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e
expm1(3M) expm1(3M)
NAME
expm1() - computes exponential functions
SYNOPSIS
#include <math.h>
double expm1(double x);
DESCRIPTION
The expm1() function is equivalent to exp(x) - 1, but may be more accurate for very small values of x.
The expm1() and log1p() functions are useful to guarantee that financial calculations of
(((1+x)**n)-1)/x,namely:
expm1(n * log1p(x))/x
are accurate when x is very small (for example, when calculating small daily interest rates).
The ISO/ANSI C committee has approved the expm1() function for inclusion in the C9X draft standard.
To use this function, compile either with the default
-Ae option or with the -Aa and -D_HPUX_SOURCE
options. Make sure your program includes <math.h>. Link in the math library by specifying
-lm on the
compiler or linker command line.
RETURN VALUE
If x is +INFINITY,
expm1() returns +INFINITY.
If x is −INFINITY,
expm1() returns -1.0.
If x is NaN,
expm1() returns NaN.
If the correct value after rounding would be smaller in magnitude than MINDOUBLE, expm1() returns
zero.
If the value overflows,
expm1() returns HUGE_VAL and sets errno to [ERANGE].
ERRORS
If expm1() fails, errno is set to the following value.
[ERANGE] The result overflows.
SEE ALSO
exp(3M), log1p(3M), math(5), values(5).
STANDARDS CONFORMANCE
expm1():XPG4.2
Section 3−−212 − 1 − HP-UX Release 11i: December 2000
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