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Интерактивная система просмотра системных руководств (man-ов)

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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 )

  • BSD mandoc
     

    NAME

    
    
    exp
    
     
    expf
    
     
    
    exp2
    
     
    exp2f
    
     
    expm1
    
     
    expm1f
    
     
    log
    
     
    logf
    
     
    log10
    
     
    log10f
    
     
    log1p
    
     
    log1pf
    
     
    pow
    
     
    powf
    
     - exponential, logarithm, power functions
    
     
    

    LIBRARY

    Lb libm
    
     
    

    SYNOPSIS

       #include <math.h>
    double exp (double x);
    float expf (float x);
    double exp2 (double x);
    float exp2f (float x);
    double expm1 (double x);
    float expm1f (float x);
    double log (double x);
    float logf (float x);
    double log10 (double x);
    float log10f (float x);
    double log1p (double x);
    float log1pf (float x);
    double pow (double x double y);
    float powf (float x float y);
     

    DESCRIPTION

    The exp ();
    and the expf ();
    functions compute the base e exponential value of the given argument Fa x .

    The exp2 ();
    and the exp2f ();
    functions compute the base 2 exponential of the given argument Fa x .

    The expm1 ();
    and the expm1f ();
    functions compute the value exp(x)-1 accurately even for tiny argument Fa x .

    The log ();
    and the logf ();
    functions compute the value of the natural logarithm of argument Fa x .

    The log10 ();
    and the log10f ();
    functions compute the value of the logarithm of argument Fa x to base 10.

    The log1p ();
    and the log1pf ();
    functions compute the value of log(1+x) accurately even for tiny argument Fa x .

    The pow ();
    and the powf ();
    functions compute the value of x to the exponent y  

    ERROR (due to Roundoff etc.)

    The values of exp (0 ,);
    expm1 (0 ,);
    exp2 (integer ,);
    and pow (integer integer);
    are exact provided that they are representable. Otherwise the error in these functions is generally below one ulp  

    RETURN VALUES

    These functions will return the appropriate computation unless an error occurs or an argument is out of range. The functions pow (x y);
    and powf (x y);
    raise an invalid exception and return an if Fa x < 0 and Fa y is not an integer. An attempt to take the logarithm of 0 will result in a divide-by-zero exception, and an infinity will be returned. An attempt to take the logarithm of a negative number will result in an invalid exception, and an will be generated.  

    NOTES

    The functions exp(x)-1 and log(1+x) are called expm1 and logp1 in BASIC on the Hewlett-Packard HP -71B and APPLE Macintosh, EXP1 and LN1 in Pascal, exp1 and log1 in C on APPLE Macintoshes, where they have been provided to make sure financial calculations of ((1+x)**n-1)/x, namely expm1(n*log1p(x))/x, will be accurate when x is tiny. They also provide accurate inverse hyperbolic functions.

    The function pow (x 0);
    returns x**0 = 1 for all x including x = 0, , and . Previous implementations of pow may have defined x**0 to be undefined in some or all of these cases. Here are reasons for returning x**0 = 1 always:

    1. Any program that already tests whether x is zero (or infinite or ) before computing x**0 cannot care whether 0**0 = 1 or not. Any program that depends upon 0**0 to be invalid is dubious anyway since that expression's meaning and, if invalid, its consequences vary from one computer system to another.
    2. Some Algebra texts (e.g. Sigler's) define x**0 = 1 for all x, including x = 0. This is compatible with the convention that accepts a[0] as the value of polynomial
      p(x) = a[0]*x**0 + a[1]*x**1 + a[2]*x**2 +...+ a[n]*x**n
      

      at x = 0 rather than reject a[0]*0**0 as invalid.

    3. Analysts will accept 0**0 = 1 despite that x**y can approach anything or nothing as x and y approach 0 independently. The reason for setting 0**0 = 1 anyway is this:
      If x(z) and y(z) are any functions analytic (expandable in power series) in z around z = 0, and if there x(0) = y(0) = 0, then x(z)**y(z) -> 1 as z -> 0.
    4. If 0**0 = 1, then **0 = 1/0**0 = 1 too; and then **0 = 1 too because x**0 = 1 for all finite and infinite x, i.e., independently of x.

     

    SEE ALSO

    fenv(3), math(3)


     

    Index

    NAME
    LIBRARY
    SYNOPSIS
    DESCRIPTION
    ERROR (due to Roundoff etc.)
    RETURN VALUES
    NOTES
    SEE ALSO


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