private bool CheckValidVariableAssignment(string lexeme)
{
if (!(SymbolTable.LookupNode(lexeme) is VariableNode))
{
CommonTools.PromptProgramErrorExit($"ERROR: Line {LexicalAnaylzer.LineNumber} Invalid " +
$"assignment to {lexeme}");
return(false);
}
return(true);
}
// Checks if an identifier exists as a variable node in symbol table and is in scope
private bool CheckDeclaredVariable()
{
if (SymbolTable.LookupNode(LexicalAnaylzer.Lexeme) == null)
{
CommonTools.PromptProgramErrorExit($"ERROR: Line {LexicalAnaylzer.LineNumber} Use of " +
$"undeclared variable {LexicalAnaylzer.Lexeme}");
return(false);
}
return(true);
}
// Inserts a node into symbol table and prints error if insertion failure
private bool InsertNode(Node node)
{
if (!SymbolTable.InsertNode(node))
{
CommonTools.PromptProgramErrorExit($"ERROR: Line {LexicalAnaylzer.LineNumber} " +
$"Duplicate lexeme \"{node.Lexeme}\" with depth \"{node.Depth}\" exists");
return(false);
}
return(true);
}
// OutputOptions -> IdentifierToken | StringLiteralToken | EndLineToken
private bool ProcessOutputOptions()
{
if (LexicalAnaylzer.Token == Token.IdentifierToken)
{
VariableNode node = (VariableNode)SymbolTable.LookupNode(LexicalAnaylzer.Lexeme);
if (node == null)
{
CommonTools.PromptProgramErrorExit($"ERROR: Line {LexicalAnaylzer.LineNumber} Use of " +
$"undeclared variable \"{LexicalAnaylzer.Lexeme}\"");
return(false);
}
if (node.Type == Token.CharToken)
{
OutputThreeAddressCode($"\t_WRC {GetThreeAddressCodeName(LexicalAnaylzer.Lexeme)}");
}
else if (node.Type == Token.IntToken)
{
OutputThreeAddressCode($"\t_WRI {GetThreeAddressCodeName(LexicalAnaylzer.Lexeme)}");
}
else
{
OutputThreeAddressCode($"\t_WRF {GetThreeAddressCodeName(LexicalAnaylzer.Lexeme)}");
}
LexicalAnaylzer.GetNextToken();
}
else if (LexicalAnaylzer.Token == Token.StringLiteralToken)
{
StringLiteralNode node = new StringLiteralNode()
{
Lexeme = $"_S{SymbolTable.StringLiteralCount}",
Literal = LexicalAnaylzer.Lexeme
};
SymbolTable.InsertNode(node);
OutputThreeAddressCode($"\t_WRS {node.Lexeme}");
LexicalAnaylzer.GetNextToken();
}
else
{
OutputThreeAddressCode($"\t_WRL");
if (!MatchToken(Token.EndLineToken))
{
return(false);
}
}
return(true);
}
public bool Start()
{
bool programCorrect = ProcessProgram() && CheckMainDeclared();
if (LexicalAnaylzer.Token != Token.EndOfFileToken && programCorrect)
{
CommonTools.PromptProgramErrorExit(
$"ERROR: Line {LexicalAnaylzer.LineNumber} " +
$"Unexpected tokens in source file, expected End-of-File Token");
}
if ((CommonTools.ThreeAddressCodeRun) && programCorrect)
{
CommonTools.WriteOutput(ThreeAddressCodeOutput);
}
return(programCorrect);
}
// InputStatement -> CharacterInToken RightShiftOperatorToken IdentifierToken InputEnd
private bool ProcessInputStatement()
{
if (!MatchToken(Token.CharacterInToken))
{
return(false);
}
if (!MatchToken(Token.RightShiftOperatorToken))
{
return(false);
}
VariableNode node = (VariableNode)SymbolTable.LookupNode(LexicalAnaylzer.Lexeme);
if (node == null)
{
CommonTools.PromptProgramErrorExit($"ERROR: Line {LexicalAnaylzer.LineNumber} Use of " +
$"undeclared variable \"{LexicalAnaylzer.Lexeme}\"");
return(false);
}
if (node.Type == Token.CharToken)
{
OutputThreeAddressCode($"\t_RDC {GetThreeAddressCodeName(LexicalAnaylzer.Lexeme)}");
}
else if (node.Type == Token.IntToken)
{
OutputThreeAddressCode($"\t_RDI {GetThreeAddressCodeName(LexicalAnaylzer.Lexeme)}");
}
else
{
OutputThreeAddressCode($"\t_RDF {GetThreeAddressCodeName(LexicalAnaylzer.Lexeme)}");
}
if (!MatchToken(Token.IdentifierToken))
{
return(false);
}
if (!ProcessInputEnd())
{
return(false);
}
return(true);
}
// Displays expected tokens error to appropriate displays
private void DisplayExpectedTokensError(string expectedToken)
{
CommonTools.PromptProgramErrorExit($"ERROR: Line {LexicalAnaylzer.LineNumber} Expected token " +
$"\"{expectedToken}\" - Received token \"{LexicalAnaylzer.Token}\"");
}
// Returns the three address code variable name of the given lexeme
private string GetThreeAddressCodeName(string lexeme)
{
decimal n;
if (decimal.TryParse(lexeme, out n))
{
string temporaryVariable;
int x;
if (int.TryParse(lexeme, out x))
{
temporaryVariable = GetTemporaryVariableName(Token.IntToken);
}
else
{
temporaryVariable = GetTemporaryVariableName(Token.FloatToken);
}
OutputThreeAddressCode($"\t{temporaryVariable} = {SignOperation}{lexeme}");
SignOperation = string.Empty;
return(temporaryVariable);
}
Node node = SymbolTable.LookupNode(lexeme);
if (node is VariableNode)
{
if (node.Depth == GlobalConfiguration.BaseDepth)
{
return($"_{lexeme}");
}
else
{
return($"_BP" + ((VariableNode)node).Offset.ToString("+0;-#"));
}
}
else if (node is ConstantNode)
{
string temporaryVariable;
if ((((ConstantNode)node).Value != null))
{
temporaryVariable = GetTemporaryVariableName(Token.IntToken);
}
else
{
temporaryVariable = GetTemporaryVariableName(Token.FloatToken);
}
string outputvalue = (((ConstantNode)node).Value ?? ((ConstantNode)node).ValueReal).ToString();
OutputThreeAddressCode($"\t{temporaryVariable} = {SignOperation}{outputvalue}");
SignOperation = string.Empty;
return(temporaryVariable);
}
else if (node is FunctionNode)
{
CommonTools.PromptProgramErrorExit($"ERROR: Line {LexicalAnaylzer.LineNumber} Invalid use function {node.Lexeme}");
return(string.Empty);
}
else
{
return(lexeme);
}
}