ultrix man page for log

exp(3m) 																   exp(3m)

Name
       exp, expm1, log, log10, log1p, pow - exponential, logarithm, power

Syntax
       #include <math.h>

       double exp(x)
       double x;

       float fexp(x)
       float x;

       double expm1(x)
       double x;

       float fexpm1(x)
       float x;

       double log(x)
       double x;

       float flog(x)
       float x;

       double log10(x)
       double x;

       float flog10(x)
       float x;

       double log1p(x)
       double x;

       float flog1p(x)
       float x;

       double pow(x,y)
       double x,y;

Description
       The and functions return the exponential function of x for double and float data types, respectively.

       The and functions return exp(x-1 accurately, including tiny x for double and float data types, respectively.

       The and functions return the natural logarithm of x for double and float data types, respectively.

       The and functions return the logarithm of x to base 10 for double and float data types, respectively.

       The and functions return log(1+x) accurately, including tiny x for double and float data types, respectively.

       The function returns x**y.

   Error (due to roundoff)
       The and functions are accurate to within an ulp, and is accurate to within approximately 2 ulps; an ulp is one Unit in the Last Place.

       The  function  is accurate to within 2 ulps when its magnitude is moderate, but becomes less accurate as the result approaches the overflow
       or underflow thresholds.  Theoretically, as these thresholds are approached, almost as many bits could be lost from the result as are indi-
       cated  in  the exponent field of the floating-point format for the resultant number.  In other words, up to 11 bits for an IEEE 754 double-
       precision floating-point number.  However, testing has never verified loss of precision as drastic as 11 bits.  The worst cases have  shown
       accuracy  of  results  to within 300 ulps for IEEE 754 double-precision floating-point numbers.	In general, a (integer, integer) result is
       exact until it is larger than 2**53 (for IEEE 754 double-precision floating-point).

Return Values
       All of the double precision functions return NaN if x or y is NaN.

       The function returns HUGE_VAL when the correct value would overflow, and zero when the correct value would underflow.

       The and functions return NaN when x is less than or equal to zero or when the correct value would overflow.

       The function returns NaN if x or y is NaN.  When both x and y are zero, 1.0 is returned.  When x is negative and y is not an  integer,  NaN
       is returned.  If x is zero and y is negative, -HUGE_VAL is returned.

       The function returns NaN when x is negative.

See Also
       math(3m)

								       RISC								   exp(3m)