Scalar output

Outputting a single scalar value

Here is a class method signature that returns a single scalar value of type Duration:

Aircraft.ETA( waypoint : Waypoint ID ) :: Duration

It might be used inside another activity like so:

current wait time = my aircraft.ETA( waypoint : /is visited next/Waypoint.ID )

Outputting multiple scalar values

To output multiple scalar values you produce a single tuple relation where the name of each output parameter is an attribute in the relation.

The method below takes as input a Tail number and returns the angle and distance to the target.

Aircraft.Trackto( target : Tail Number ) :: ( angle : Degrees, distance : Meters )

The corresponding action language within the method looks like this:

// compute using in.target input parameter and
// assign results to data variables a and d

=>> ( angle: a, distance: d )

The =>> symbol defines an output within an activity.