
atan(+Number, -Result)

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

    Result is atan(Number)

    which should be preferred for portability.

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




Modes and Determinism
   atan(+, -) is det

Exceptions
     4 --- Number is not instantiated (non-coroutining mode only).
    24 --- Number is not of a numeric type.

Examples
   
    Result is atan(0.0).		% gives Result = 0.0
    Result is atan(1.0).		% gives Result = 0.785398
    Result is atan(-8).			% gives Result = -1.44644


See Also
   is / 2
