SubtypeDeclaration ParseSubtypeDeclaration()
{
ReadNextToken(); //skip subtype
string identifier = fCurrentToken.Value;
ReadNextToken(); //skip identifier
fCurrentToken = fLexicalAnalyser.SkipExpected(TokenType.Word, "is");
SubtypeIndication subtype = ParseSubtypeIndication();
//Read until end of line
fCurrentToken = fLexicalAnalyser.SkipExpected(TokenType.Symbol, ";");
SubtypeDeclaration ParsedSubtype = new SubtypeDeclaration(identifier, subtype);
SubtypeList.Add(ParsedSubtype);
return(ParsedSubtype);
}
// This method is for determining the specified attribute for a type.
// Currently only 3 attributes have been defined (left, right and length).
// Attributes can be called on types or subtypes, therefore cases for each are specified below.
int DetermineAttribute(string Attribute, string Type)
{
// It is first determined whether the subtype passed exists in the list of subtypes.
if (SubtypeList.Exists(x => x.Identifier == Type))
{
// The subtype is found and stored in chosenType.
SubtypeDeclaration chosenType = SubtypeList.Find(x => x.Identifier == Type);
// The correct attribute is fetched depending on the passed string.
if (Attribute == "left")
{
return(chosenType.Left);
}
if (Attribute == "right")
{
return(chosenType.Right);
}
if (Attribute == "high")
{
return((chosenType.Right >= chosenType.Left) ? chosenType.Right : chosenType.Left);
}
if (Attribute == "low")
{
return(chosenType.Right >= chosenType.Left ? chosenType.Left : chosenType.Right);
}
if (Attribute == "length")
{
return(Math.Abs(chosenType.Left - chosenType.Right) + 1);
}
throw new ParserException("Attribute Provided is not recognised: " + Attribute);
}
else if (EnumerationTypeList.Exists(x => x.Identifier == Type))
{
EnumerationTypeDeclaration chosenType = EnumerationTypeList.Find(x => x.Identifier == Type);
if (Attribute == "left")
{
return(chosenType.Left);
}
if (Attribute == "right")
{
return(chosenType.Right);
}
if (Attribute == "length")
{
return(Math.Abs(chosenType.Left - chosenType.Right) + 1);
}
throw new ParserException("Attribute Provided is not recognised");
}
// If the type passed is neither a subtype or a type an exception is thrown.
else
{
throw new ParserException("Cannot determine attribute, Type/Subtype not recognized.");
}
}