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exp (3)
  • exp (3) ( Solaris man: Библиотечные вызовы )
  • exp (3) ( FreeBSD man: Библиотечные вызовы )
  • exp (3) ( Русские man: Библиотечные вызовы )
  • exp (3) ( Linux man: Библиотечные вызовы )
  • >> exp (3) ( POSIX man: Библиотечные вызовы )
  •  

    NAME

    exp, expf, expl - exponential function
     
    

    SYNOPSIS

    #include <math.h>

    double exp(double x);
    float expf(float
    x);
    long double expl(long double
    x);
     

    DESCRIPTION

    The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.

    These functions shall compute the base- e exponential of x.

    An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.  

    RETURN VALUE

    Upon successful completion, these functions shall return the exponential value of x.

    If the correct value would cause overflow, a range error shall occur and exp(), expf(), and expl() shall return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.

    If the correct value would cause underflow, and is not representable, a range error may occur, and  either 0.0 (if supported), or  an implementation-defined value shall be returned.

    If x is NaN, a NaN shall be returned.

    If x is ±0, 1 shall be returned.

    If x is -Inf, +0 shall be returned.

    If x is +Inf, x shall be returned.

    If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.  

    ERRORS

    These functions shall fail if:

    Range Error
    The result overflows.

    If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.

    These functions may fail if:

    Range Error
    The result underflows.

    If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

    The following sections are informative.  

    EXAMPLES

    None.  

    APPLICATION USAGE

    Note that for IEEE Std 754-1985 double, 709.8 < x implies exp( x) has overflowed. The value x < -708.4 implies exp( x) has underflowed.

    On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.  

    RATIONALE

    None.  

    FUTURE DIRECTIONS

    None.  

    SEE ALSO

    feclearexcept() , fetestexcept() , isnan() , log() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions, <math.h>  

    COPYRIGHT

    Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications 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 Standard, 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 .


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUE
    ERRORS
    EXAMPLES
    APPLICATION USAGE
    RATIONALE
    FUTURE DIRECTIONS
    SEE ALSO
    COPYRIGHT


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