
atan(+Number, ?Result)

   Evaluates the trigonometric function atan(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 atan(Number, Result) is
   equivalent to

    Result is atan(Number)

    which should be preferred for portability.

   In coroutining mode, if Number is a free variable, the call to atan/2 is
   delayed until this variable is instantiated.




Resatisfiable
      No

Fail Conditions
      Fails if the result of the evaluation does not unify with Result.



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.

Examples
   
Success:
      atan(0.0, 0.0).
      atan(1.0, Result).       (gives Result = 0.785398)
      atan(-8, Result).        (gives Result = -1.44644)
Fail:
      atan(1, 0.0).
Error:
      atan(A, 6.0).                   (Error 4).
      atan(1.55741, 1).               (Error 5).
      atan(1 + 0.55741, 1.0).         (Error 24).
      atan(5, r).                     (Error 24).





See Also
   is / 2
