Command:

EXPM1(3P) POSIX Programmer's Manual EXPM1(3P)PROLOGThis manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may dif- fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.NAMEexpm1, expm1f, expm1l - compute exponential functionsSYNOPSIS#include<math.h>doubleexpm1(doublex);floatexpm1f(floatx);longdoubleexpm1l(longdoublex);DESCRIPTIONThese functions shall computee**x-1.0. An application wishing to check for error situations should seterrnoto zero and callfeclearex-cept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.RETURNVALUEUpon successful completion, these functions returne**x-1.0. If the correct value would cause overflow, a range error shall occur andexpm1(),expm1f(), andexpm1l() shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively. Ifxis NaN, a NaN shall be returned. Ifxis ?0, ?0 shall be returned. Ifxis -Inf, -1 shall be returned. Ifxis +Inf,xshall be returned. Ifxis subnormal, a range error may occur andxshould be returned.ERRORSThese functions shall fail if: Range Error The result overflows. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, thenerrnoshall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point excep- tion shall be raised. These functions may fail if: Range Error The value ofxis subnormal. If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, thenerrnoshall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.Thefollowingsectionsareinformative.EXAMPLESNone.APPLICATIONUSAGEThe value ofexpm1(x) may be more accurate thanexp(x)-1.0 for small values ofx. Theexpm1() andlog1p() functions are useful for financial calculations of ((1+x)**n-1)/x, namely:expm1(n*log1p(x))/xwhenxis very small (for example, when calculating small daily interest rates). These functions also simplify writing accurate inverse hyperbolic functions. For IEEE Std 754-1985double, 709.8 <ximpliesexpm1(x) has overflowed. On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are indepen- dent of each other, but at least one of them must be non-zero.RATIONALENone.FUTUREDIRECTIONSNone.SEEALSOexp(),feclearexcept(),fetestexcept(),ilogb(),log1p(), the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions,<math.h>COPYRIGHTPortions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan- dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifica- tions Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan- dard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html . IEEE/The Open Group 2003 EXPM1(3P)