/// <summary>
/// Provides the surface of this function if it has been statically defined
/// </summary>
/// <param name="context">the context used to create the surface</param>
/// <param name="xParam">The X axis of this surface</param>
/// <param name="yParam">The Y axis of this surface</param>
/// <param name="explain"></param>
/// <returns>The surface which corresponds to this expression</returns>
public override Surface CreateSurface(InterpretationContext context, Parameter xParam, Parameter yParam,
ExplanationPart explain)
{
Surface retVal = base.CreateSurface(context, xParam, yParam, explain);
Surface surface = InitialValue.CreateSurface(context, xParam, yParam, explain);
if (surface != null)
{
ListValue value = ListExpression.GetValue(context, explain) as ListValue;
if (value != null)
{
int token = PrepareIteration(context);
AccumulatorVariable.Value = surface.Function;
foreach (IValue v in value.Val)
{
if (v != EfsSystem.Instance.EmptyValue)
{
// All elements should always be != from EmptyValue
ElementFound = true;
IteratorVariable.Value = v;
if (ConditionSatisfied(context, explain))
{
MatchingElementFound = true;
AccumulatorVariable.Value = IteratorExpression.GetValue(context, explain);
}
}
NextIteration();
}
Function function = AccumulatorVariable.Value as Function;
if (function != null)
{
retVal = function.Surface;
}
else
{
throw new Exception("Expression does not reduces to a function");
}
EndIteration(context, explain, token);
}
}
else
{
throw new Exception("Cannot create surface for initial value " + InitialValue);
}
retVal.XParameter = xParam;
retVal.YParameter = yParam;
return(retVal);
}