SignalType ParseTypeDeclaration()
{
ReadNextToken(); //skip type
SignalType fType;
string identifier = fCurrentToken.Value;
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Word, "is");
if (fCurrentToken.Equals(TokenType.Word, "array"))
{
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Symbol, "(");
Node from = ParseExpression();
//Used to have skip over "to" here but it can also be "downto"
ReadNextToken();
Node to = ParseExpression();
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Word, "of");
string subtypeIndication = fCurrentToken.Value;
fType = FindDefinedType();
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Symbol, ";");
ArrayTypeDeclaration ParsedArrayType = new ArrayTypeDeclaration(identifier, from.Eval(), to.Eval(), fType);
ArrayTypeList.Add(ParsedArrayType);
return(ParsedArrayType);
}
else if (fCurrentToken.Equals(TokenType.Word, "record"))
{
List <string> identifierList = new List <string> ();
List <SignalType> subtypeIndicationList = new List <SignalType> ();
ReadNextToken(); //skip "record"
CheckForUnexpectedEndOfSource();
while (!fCurrentToken.Equals(TokenType.Word, "end"))
{
identifierList.Add(fCurrentToken.Value);
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Symbol, ":");
//Searches for the type of each record entry.
fType = FindDefinedType();
subtypeIndicationList.Add(fType);
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Symbol, ";");
}
//Skip Over: end record;
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Symbol, ";");
RecordTypeDeclaration ParsedRecordType = new RecordTypeDeclaration(identifier, identifierList, subtypeIndicationList);
RecordTypeList.Add(ParsedRecordType);
return(ParsedRecordType);
}
else
{
List <string> enumerationList = new List <string> ();
fCurrentToken = fLexicalAnalyser.SkipOver(TokenType.Symbol, "(");
while (!fCurrentToken.Equals(TokenType.Symbol, ";"))
{
enumerationList.Add(fCurrentToken.Value);
//Can't use skip over "," since no "," after last entry
ReadNextToken();
ReadNextToken();
}
ReadNextToken();
EnumerationTypeDeclaration ParsedEnumerationType = new EnumerationTypeDeclaration(identifier, enumerationList);
EnumerationTypeList.Add(ParsedEnumerationType);
return(ParsedEnumerationType);
}
}
// 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.");
}
}
