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log (3)
  • log (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • >> log (3) ( Solaris man: Библиотечные вызовы )
  • log (3) ( FreeBSD man: Библиотечные вызовы )
  • log (3) ( Русские man: Библиотечные вызовы )
  • log (3) ( Linux man: Библиотечные вызовы )
  • log (3) ( POSIX man: Библиотечные вызовы )
  • log (7) ( Solaris man: Макропакеты и соглашения )
  • log (9) ( FreeBSD man: Ядро )
  • Ключ log обнаружен в базе ключевых слов.
  •  

    NAME

    log, logf, logl - natural logarithm function
     
    

    SYNOPSIS

    c99 [ flag... ] file... -lm [ library... ]
    #include <math.h>
    
    double log(double x);
    

    float logf(float x);
    

    long double logl(long double x);
    

     

    DESCRIPTION

    These functions compute the natural logarithm of their argument x, log(e)(x).  

    RETURN VALUES

    Upon successful completion, log() returns the natural logarithm of x.

    If x is ±0, a pole error occurs and log(), logf(), and logl() return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

    For finite values of x that are less than 0, or if x is -Inf, a domain error occurs and a NaN is returned.

    If x is NaN, a NaN is returned.

    If x is 1, +0 is returned.

    If x is +Inf, x is returned.

    For exceptional cases, matherr(3M) tabulates the values to be returned by log() as specified by SVID3 and XPG3.  

    ERRORS

    These functions will fail if:

    Domain Error

    The finite value of x is negative, or x is -Inf.

    If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the invalid floating-point exception is raised.

    The log() function sets errno to EDOM if the value of x is negative.

    Pole Error

    The value of x is 0.

    If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the divide-by-zero floating-point exception is raised.

     

    USAGE

    An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.

    An application can also set errno to 0 before calling log(). On return, if errno is non-zero, an error has occurred. The logf() and logl() functions do not set errno.  

    ATTRIBUTES

    See attributes(5) for descriptions of the following attributes:

    ATTRIBUTE TYPEATTRIBUTE VALUE

    Interface StabilityStandard

    MT-Level

     

    SEE ALSO

    exp(3M), feclearexcept(3M), fetestexcept(3M), isnan(3M), log10(3M), log1p(3M), math.h(3HEAD), matherr(3M), attributes(5), standards(5)


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    ERRORS
    USAGE
    ATTRIBUTES
    SEE ALSO


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