log
This function Returns the natural logarithm of x.
double log(double x)
Parameters:
x
The number to convert.
Return value:
Natural logarithm of x, for values of x greater than zero. If x is 0 or less, the function will return 0.
Remarks:
The natural logarithm is the base-e logarithm, the inverse of the natural exponential function (exponent). For base-10 logarithms, please see log10.
Example:

    void main()
    {
    double param=5.5;
    double result=log(param);
    alert("log test", "log "+param+" is "+result+".");
    }