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expm1d64.3m (2010 09)

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expm1d64(3M) expm1d64(3M)
(HP Integrity Server Only)
NAME
expm1d64(), expm1d128(), expm1d32() - decimal exponential minus 1 functions
SYNOPSIS
#define __STDC_WANT_DEC_FP__
#include <math.h>
_Decimal64 expm1d64(_Decimal64 x);
_Decimal128 expm1d128(_Decimal128 x);
_Decimal32 expm1d32(_Decimal32 x);
DESCRIPTION
The expm1d64() function is equivalent to expd64(x
)-1, but may be more accurate for very small
values of x.
The
expm1d64() and log1pd64() functions are useful to guarantee that financial calculations of
(((1+x)**n)-1)/x are accurate when x is very small, namely:
expm1d64(n * log1pd64(x))/x
The preceding example might be applicable when calculating small daily interest rates.
expm1d128() is a _Decimal128 version of expm1d64(); it takes a _Decimal128 argument and
returns a _Decimal128 result.
expm1d32() is a _Decimal32 version of expm1d64(); it takes a _Decimal32 argument and
returns a _Decimal32 result.
These math functions are supported for HP-UX 11i Version 3 September 2008 Update and forward.
USAGE
To use any of these functions, compile with the +decfp option.
Make sure your program defines
__STDC_WANT_DEC_FP__
and then includes <math.h>.
Link in the math library by specifying
-lm or -l:libm.a on the linking command line.
For more information, see the HP-UX floating-point guide for HP Integrity servers at the following site:
http://www.hp.com/go/fp
.
RETURN VALUE
expm1d64(±0) returns ±0.
If x is +infinity,
expm1d64() returns +infinity.
If x is −infinity,
expm1d64() returns -1.
If x is NaN,
expm1d64() returns a quiet NaN.
expm1d64() returns +infinity (or, in some non-default rounding direction modes, the maximum finite
number) in lieu of a value whose magnitude is too large, and raises the overflow and inexact exceptions.
expm1d64() raises the underflow exception whenever a result is tiny (essentially subnormal or zero)
and inexact.
expm1d64() raises the inexact exception whenever a rounded result does not equal the mathematical
result.
ERRORS
If the correct value would overflow,
expm1d64() sets errno to [ERANGE].
SEE ALSO
annuity(3M), cbrtd64(3M), compound(3M), exp10d64(3M), exp2d64(3M), expd64(3M), log1pd64(3M),
powd64(3M), sqrtd64(3M), math(5).
STANDARDS CONFORMANCE
These functions conform to ISO/IEC TR 24732, "Extension for the programming language C to support
decimal floating-point arithmetic".
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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