
ln(+Number, -Result)

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



Arguments
   Number              A number.
   Result              A variable 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).
     5 --- Result is a number but not a float or breal.
    24 --- Number is not of a numeric type.
    24 --- Result is neither a number nor a variable.
    20 --- Illegal arithmetic operation:  Number is 0 or less.

Examples
   
Success:
      ln(2.0, Result).          (gives Result = 0.693147)
      ln(1, Result).            (gives Result = 0.0)
Fail:
      ln(1, 1.0).
Error:
      ln(A, 6.0).                   (Error 4).
      ln(1, 0).                     (Error 5).
      ln(-2, Result).               (Error 20).
      ln(0, Result).                (Error 20).
      ln(4 + 2, 1.79176).           (Error 24).
      ln(1, r).                     (Error 24).





See Also
   is / 2
