/// <summary>
/// Provides the value of the function
/// </summary>
/// <param name="context"></param>
/// <param name="actuals">the actual parameters values</param>
/// <param name="explain"></param>
/// <returns>The value for the function application</returns>
public override IValue Evaluate(InterpretationContext context, Dictionary <Actual, IValue> actuals,
ExplanationPart explain)
{
IValue retVal = EFSSystem.BoolType.False;
int token = context.LocalScope.PushContext();
AssignParameters(context, actuals);
ListValue collection = context.FindOnStack(Collection).Value as ListValue;
if (collection != null)
{
IValue expectedFirst = context.FindOnStack(ExpectedFirst).Value;
if (expectedFirst != null)
{
int firstIndex = collection.Val.IndexOf(expectedFirst);
if (firstIndex >= 0)
{
IValue expectedSecond = context.FindOnStack(ExpectedSecond).Value;
if (expectedSecond != null)
{
int secondIndex = collection.Val.IndexOf(expectedSecond);
if (secondIndex >= 0)
{
if (firstIndex < secondIndex)
{
retVal = EFSSystem.BoolType.True;
}
}
else
{
Collection.AddError("Cannot find " + expectedSecond.FullName + " in " +
collection.ToString() + " to evaluate " + Name);
}
}
else
{
Collection.AddError("Cannot evaluate second element to evaluate " + Name);
}
}
else
{
Collection.AddError("Cannot find " + expectedFirst.FullName + " in " + collection.ToString() +
" to evaluate " + Name);
}
}
else
{
Collection.AddError("Cannot evaluate first element to evaluate " + Name);
}
}
context.LocalScope.PopContext(token);
return(retVal);
}