Syntax	ln ( r : real ) : real
Description	The ln function is used to find the natural logarithm (base e) of a number. For example, ln ( 1) is 0.
Example	This program prints out the logarithms of 1, 2, 3, … up to 100. for i : 1 .. 100 put "Logarithm of ", i, " is ", ln ( i ) end for
Details	See also the exp (exponential) function. You cannot take the logarithm of zero or a negative number.
Note	logn (i ) = ln (i ) / ln (n )
See also	exp (the exponentiation function). See also predefined unit Math.