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expm1 (3)
  • expm1 (3) ( Solaris man: Библиотечные вызовы )
  • expm1 (3) ( FreeBSD man: Библиотечные вызовы )
  • expm1 (3) ( Русские man: Библиотечные вызовы )
  • >> expm1 (3) ( Linux man: Библиотечные вызовы )
  • expm1 (3) ( POSIX man: Библиотечные вызовы )
  •  

    NAME

    expm1, expm1f, expm1l - exponential minus 1
     
    

    SYNOPSIS

    #include <math.h>
    
    double expm1(double x);
    
    float expm1f(float x);
    long double expm1l(long double x);
    Link with -lm.

    Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

    expm1(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or cc -std=c99
    expm1f(), expm1l(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99  

    DESCRIPTION

    expm1(x) returns a value equivalent to
    
        exp(x) - 1
    
    
    It is computed in a way that is accurate even if the value of x is near zero---a case where exp(x) - 1 would be inaccurate due to subtraction of two numbers that are nearly equal.  

    RETURN VALUE

    On success, these functions return exp(x) - 1.

    If x is a NaN, a NaN is returned.

    If x is +0 (-0), +0 (-0) is returned.

    If x is positive infinity, positive infinity is returned.

    If x is negative infinity, -1 is returned.

    If the result overflows, a range error occurs, and the functions return -HUGE_VAL, -HUGE_VALF, or -HUGE_VALL, respectively.  

    ERRORS

    See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

    The following errors can occur:

    Range error, overflow
    An overflow floating-point exception (FE_OVERFLOW) is raised.

    These functions do not set errno.  

    CONFORMING TO

    C99, POSIX.1-2001.  

    BUGS

    For some large negative x values (where the function result approaches -1), expm1() raises a bogus underflow floating-point exception.

    For some large positive x values, expm1() raises a bogus invalid floating-point exception in addition to the expected overflow exception, and returns a NaN instead of positive infinity.  

    SEE ALSO

    exp(3), log(3), log1p(3)  

    COLOPHON

    This page is part of release 3.14 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUE
    ERRORS
    CONFORMING TO
    BUGS
    SEE ALSO
    COLOPHON


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