
ln(+Number, -Result)

   Evaluates the natural logarithm ln(Number) and unifies the resulting value
with Result.



Arguments
   Number              A number.
   Result              Output: float or breal.

Type
   Arithmetic

Description
   This predicate is used by the ECLiPSe compiler to expand evaluable
   arithmetic expressions.  So the call to ln(Number, Result) is equivalent
   to

    Result is ln(Number)

    which should be preferred for portability.

   In coroutining mode, if Number is uninstantiated, the call to ln/2 is
   delayed until this variable is instantiated.




Modes and Determinism
   ln(+, -) is det

Exceptions
     4 --- Number is not instantiated (non-coroutining mode only).
    24 --- Number is not of a numeric type.
    20 --- Illegal arithmetic operation:  Number is 0 or less.

Examples
   
Success:
    Result is ln(2.0).          % gives Result = 0.693147
    Result is ln(1).            % gives Result = 0.0

Error:
    Result is ln(-2).           % arithmetic exception
    Result is ln(0).            % arithmetic exception


See Also
   is / 2
