/// <summary>
        /// Provides the graph of this function if it has been statically defined
        /// </summary>
        /// <param name="context">the context used to create the graph</param>
        /// <returns></returns>
        public override Graph createGraph(Interpreter.InterpretationContext context, Parameter parameter)
        {
            Graph retVal = null;

            Graph    MRSPGraph        = null;
            Function speedRestriction = context.findOnStack(SpeedRestrictions).Value as Function;

            if (speedRestriction != null)
            {
                Parameter p = (Parameter)speedRestriction.FormalParameters[0];

                int token = context.LocalScope.PushContext();
                context.LocalScope.setGraphParameter(p);
                MRSPGraph = createGraphForValue(context, context.findOnStack(SpeedRestrictions).Value, p);
                context.LocalScope.PopContext(token);
            }

            if (MRSPGraph != null)
            {
                Function deceleratorFactor = context.findOnStack(DecelerationFactor).Value as Function;
                if (deceleratorFactor != null)
                {
                    Surface DecelerationSurface = deceleratorFactor.createSurface(context);
                    if (DecelerationSurface != null)
                    {
                        FlatSpeedDistanceCurve           MRSPCurve           = MRSPGraph.FlatSpeedDistanceCurve(MRSPGraph.ExpectedEndX());
                        AccelerationSpeedDistanceSurface accelerationSurface = DecelerationSurface.createAccelerationSpeedDistanceSurface(double.MaxValue, double.MaxValue);
                        QuadraticSpeedDistanceCurve      BrakingCurve        = null;
                        try
                        {
                            BrakingCurve = EtcsBrakingCurveBuilder.Build_A_Safe_Backward(accelerationSurface, MRSPCurve);
                        }
                        catch (System.Exception e)
                        {
                            retVal = new Graph();
                            retVal.addSegment(new Graph.Segment(0, double.MaxValue, new Graph.Segment.Curve(0, 0, 0)));
                        }

                        if (BrakingCurve != null)
                        {
                            retVal = new Graph();

                            // TODO : Remove the distinction between linear curves and quadratic curves
                            bool isLinear = true;
                            for (int i = 0; i < BrakingCurve.SegmentCount; i++)
                            {
                                QuadraticCurveSegment segment = BrakingCurve[i];
                                if (segment.A.ToUnits() != 0.0 || segment.V0.ToUnits() != 0.0)
                                {
                                    isLinear = false;
                                    break;
                                }
                            }

                            for (int i = 0; i < BrakingCurve.SegmentCount; i++)
                            {
                                QuadraticCurveSegment segment = BrakingCurve[i];

                                Graph.Segment newSegment;
                                if (isLinear)
                                {
                                    newSegment = new Graph.Segment(
                                        segment.X.X0.ToUnits(),
                                        segment.X.X1.ToUnits(),
                                        new Graph.Segment.Curve(0.0, segment.V0.ToSubUnits(SiSpeed_SubUnits.KiloMeter_per_Hour), 0.0));
                                }
                                else
                                {
                                    newSegment = new Graph.Segment(
                                        segment.X.X0.ToUnits(),
                                        segment.X.X1.ToUnits(),
                                        new Graph.Segment.Curve(
                                            segment.A.ToSubUnits(SiAcceleration_SubUnits.Meter_per_SecondSquare),
                                            segment.V0.ToSubUnits(SiSpeed_SubUnits.KiloMeter_per_Hour),
                                            segment.D0.ToSubUnits(SiDistance_SubUnits.Meter)
                                            )
                                        );
                                }
                                retVal.addSegment(newSegment);
                            }
                        }
                    }
                    else
                    {
                        Log.Error("Cannot create surface for " + DecelerationFactor.ToString());
                    }
                }
                else
                {
                    Log.Error("Cannot evaluate " + DecelerationFactor.ToString() + " as a function");
                }
            }
            else
            {
                Log.Error("Cannot create graph for " + SpeedRestrictions.ToString());
            }

            return(retVal);
        }
        /// <summary>
        ///     Creates a graph for the function
        /// </summary>
        /// <param name="context"></param>
        /// <param name="parameter"></param>
        /// <param name="explain"></param>
        /// <returns></returns>
        public override Graph CreateGraph(InterpretationContext context, Parameter parameter, ExplanationPart explain)
        {
            Graph retVal = new Graph();

            StructureValue LocationStruct = context.FindOnStack(Target).Value as StructureValue;

            SiDistance location;
            SiSpeed    speed;

            if (LocationStruct != null)
            {
                IVariable locationField = LocationStruct.Val["Location"] as IVariable;
                location = new SiDistance((locationField.Value as DoubleValue).Val);
                IVariable speedField = LocationStruct.Val["Speed"] as IVariable;
                speed = new SiSpeed((speedField.Value as DoubleValue).Val, SiSpeed_SubUnits.KiloMeter_per_Hour);

                Function decelerationFactor = context.FindOnStack(DecelerationFactor).Value as Function;
                if (decelerationFactor != null)
                {
                    Surface DecelerationSurface = decelerationFactor.CreateSurface(context, explain);
                    if (DecelerationSurface != null)
                    {
                        AccelerationSpeedDistanceSurface accelerationSurface =
                            DecelerationSurface.createAccelerationSpeedDistanceSurface(double.MaxValue, double.MaxValue);

                        QuadraticSpeedDistanceCurve BrakingCurve = null;

                        try
                        {
                            BrakingCurve = EtcsBrakingCurveBuilder.Build_Deceleration_Curve(accelerationSurface, speed,
                                                                                            location);
                        }
                        catch (Exception e)
                        {
                            retVal.AddSegment(new Graph.Segment(0, double.MaxValue, new Graph.Segment.Curve(0, 0, 0)));
                        }

                        SiSpeed finalSpeed = new SiSpeed(GetDoubleValue(context.FindOnStack(EndSpeed).Value),
                                                         SiSpeed_SubUnits.KiloMeter_per_Hour);
                        for (int i = 0; i < BrakingCurve.SegmentCount; i++)
                        {
                            QuadraticCurveSegment segment = BrakingCurve[i];

                            SiSpeed endSpeed = Max(finalSpeed, segment.Get(segment.X.X1));

                            SiDistance endDistance;
                            if (endSpeed == finalSpeed)
                            {
                                // Ensures that a braking curve is calculated until the finalSpeed
                                // but not further than the end of the curve segment
                                SiSpeed tmp = Max(segment.Get(segment.X.X1),
                                                  endSpeed - new SiSpeed(0.001));
                                endDistance = segment.IntersectAt(tmp);
                            }
                            else
                            {
                                endDistance = segment.X.X1;
                            }

                            Graph.Segment newSegment = new Graph.Segment(
                                segment.X.X0.ToUnits(),
                                endDistance.ToUnits(),
                                new Graph.Segment.Curve(
                                    segment.A.ToSubUnits(SiAcceleration_SubUnits.Meter_per_SecondSquare),
                                    segment.V0.ToSubUnits(SiSpeed_SubUnits.KiloMeter_per_Hour),
                                    segment.D0.ToSubUnits(SiDistance_SubUnits.Meter)
                                    )
                                );
                            retVal.AddSegment(newSegment);

                            if (endSpeed == finalSpeed)
                            {
                                break;
                            }
                        }
                    }
                }
            }
            return(retVal);
        }