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atan(+Number, -Result)

Evaluates the trigonometric function atan(Number) and unifies the resulting value with Result.
A number.
Output: float or breal.


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


(4) instantiation fault
Number is not instantiated (non-coroutining mode only).
(24) number expected
Number is not of a numeric type.


    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