/// <summary>
/// Create a binary expression
/// </summary>
public SyntaxExpr(Token function, SyntaxExpr param1, SyntaxExpr param2)
{
mParameters = new List <SyntaxExpr>();
mFunction = function;
mParameters.Add(param1);
mParameters.Add(param2);
}
/// <summary>
/// Make a bit declaration. First parameter is declaration (with optional
/// array parameter). Second parameter is optional assignment.
/// </summary>
public SyntaxExpr ParseBitStatement(string[] rejects)
{
// Create "bit" statement
SyntaxExpr expr = new SyntaxExpr(Accept("bit"));
if (mToken.Type != eTokenType.Identifier)
{
Reject("Expecting a variable name", rejects);
return(expr);
}
// Create declaration (array size is optional parameter)
Token variableName = Accept();
SyntaxExpr declaration = new SyntaxExpr(variableName);
if (mTokenName == "[")
{
declaration.AddParam(ParseParen());
}
// First parameter is declaration
expr.AddParam(declaration);
// Second parameter (optional) is assignment statement
if (mTokenName == "=")
{
expr.AddParam(new SyntaxExpr(Accept(), new SyntaxExpr(variableName), ParseExpr()));
}
return(expr);
}
/// <summary>
/// Parse multiple statements until 'box', 'end', 'else', or 'elif'
/// is found. Returns the statements that are parsed.
/// Adds declarations to the box locals. Never returns NULL.
/// </summary>
public SyntaxExpr ParseStatements(SyntaxBox box, bool topLevel)
{
// Create an "{" expression, which (for now means "statements")
SyntaxExpr statements = new SyntaxExpr(mInternalTokenStatement);
// While not end of file and not end of box and not new box
while (mTokenName != "" &&
mTokenName != "box" &&
mTokenName != "end" &&
mTokenName != "else" &&
mTokenName != "elif")
{
// Skip blank statements
while (mTokenName == ";")
{
Accept();
}
// Parse the statement
SyntaxExpr statement = ParseStatement(box, topLevel);
if (statement != null)
{
statements.AddParam(statement);
}
while (mTokenName == ";")
{
Accept();
}
}
return(statements);
}
/// <summary>
/// Parse a constant declaration (only "int" type is supported)
/// </summary>
SyntaxExpr ParseConstStatement()
{
// Create "const" statement
SyntaxExpr expr = new SyntaxExpr(Accept("const"));
if (mTokenName != "int")
{
Reject("Expecting keyword 'int'", REJECT_LINE);
return(expr);
}
// First parameter is the type, "int"
expr.AddParam(new SyntaxExpr(Accept()));
// Variable name must be identifier
if (mToken.Type != eTokenType.Identifier)
{
Reject("Expecting a variable name", REJECT_LINE);
return(expr);
}
Token variableName = Accept();
// Const statement requires an assignment
if (mTokenName != "=")
{
Reject("Expecting '=' - Assignment is required");
return(expr);
}
// Second parameter is the assignment expression
expr.AddParam(new SyntaxExpr(Accept(), new SyntaxExpr(variableName), ParseExpr()));
return(expr);
}
/// <summary>
/// Append a parameter to the parameters list.
/// </summary>
public void AddParam(SyntaxExpr e)
{
if (mParameters == null)
{
mParameters = new List <SyntaxExpr>();
}
mParameters.Add(e);
}
/// <summary>
/// Parse an array or function call
/// </summary>
SyntaxExpr ParseExprArrayOrFunction()
{
SyntaxExpr result = ParseExprAtom();
if (mTokenName == "(" || mTokenName == "[")
{
result = ParseParameters(result);
}
return(result);
}
/// <summary>
/// Parse an expression
/// </summary>
public SyntaxExpr ParseExpr()
{
SyntaxExpr result = ParseExprTernary();
// Optionally build a range function
if (mTokenName == ":" || mTokenName == "..")
{
return(new SyntaxExpr(Accept(), result, ParseExprTernary()));
}
return(result);
}
/// <summary>
/// Parse equality
/// </summary>
SyntaxExpr ParseExprCompare()
{
SyntaxExpr result = ParseExprPlus();
// Optionally build equality function
if (mTokenName == "==" || mTokenName == "!=")
{
return(new SyntaxExpr(Accept(), result, ParseExprPlus()));
}
return(result);
}
/// <summary>
/// Parse (*, /, %)
/// </summary>
SyntaxExpr ParseExprMult()
{
SyntaxExpr result = ParseUnary();
// Build multiplication function
while (mTokenName == "*" || mTokenName == "/" || mTokenName == "%")
{
result = new SyntaxExpr(Accept(), result, ParseUnary());
}
return(result);
}
/// <summary>
/// Parse (+, -)
/// </summary>
SyntaxExpr ParseExprPlus()
{
SyntaxExpr result = ParseExprXor();
// Build addition function
while (mTokenName == "+" || mTokenName == "-")
{
result = new SyntaxExpr(Accept(), result, ParseExprXor());
}
return(result);
}
/// <summary>
/// Parse an if statement (expects 'if' at the input)
/// </summary>
SyntaxExpr ParseIfStatement(SyntaxBox box)
{
// Parse "if" token, condition, and statements
Token ifToken = mToken;
Accept("if");
SyntaxExpr ifExpr = new SyntaxExpr(ifToken);
ifExpr.AddParam(ParseIfCond());
ifExpr.AddParam(ParseStatements(box, false));
// Parse "elif" statements
SyntaxExpr elseExpr = ifExpr;
while (mTokenName == "elif")
{
// Parse "elif" token, condition, and statements
// NOTE: "elif" token is converted to "if"
Connect(ifToken, mToken);
Accept("elif");
SyntaxExpr newIf = new SyntaxExpr(ifToken);
newIf.AddParam(ParseIfCond());
newIf.AddParam(ParseStatements(box, false));
// Convert the new "elif" to "else if"
elseExpr.AddParam(newIf);
elseExpr = newIf;
}
// Parse the "else" clause (if it exists)
if (mTokenName == "else")
{
Connect(ifToken, mToken);
Accept("else");
elseExpr.AddParam(ParseStatements(box, false));
}
// Parse end of box statement
if (mTokenName == "end")
{
mToken.InfoString = "end if";
Connect(ifToken, mToken);
Accept();
}
else
{
Reject("Expecting 'end' - end of if statement body", REJECT_BOX);
}
// Parse "else" part
return(ifExpr);
}
/// <summary>
/// Parse parameters '(' param1 ',' param2 ... ')'
/// NOTE: firstParam is the function name, and will be the first
/// parameter of the result. The open and close '()' or '[]' will
/// be connected.
/// </summary>
SyntaxExpr ParseParameters(SyntaxExpr firstParam)
{
// Read open '(' or '['
Token openToken = mToken;
if (openToken != "(" && openToken != "[")
{
throw new Exception("Compiler error: Expecting '(' or '[' while parsing parameters");
}
// Create an expression with '(' or '['
SyntaxExpr result = new SyntaxExpr(Accept(), firstParam);
string tokenExpected = openToken == "(" ? ")" : "]";
string [] rejectTokens = openToken == "(" ? REJECT_PAREN : REJECT_BRACKET;
// Empty () function call?
if (mTokenName == tokenExpected)
{
// Return an empty () or []
Connect(openToken, mToken);
Accept();
return(result);
}
// Parse all parameters
result.AddParam(ParseExpr());
while (mTokenName == ",")
{
Accept();
result.AddParam(ParseExpr());
}
// If not ended properly, reject this expression
if (mTokenName != tokenExpected)
{
// The rest of the line is rejected
Reject("Expecting '" + tokenExpected + "' or ','", rejectTokens);
}
if (mTokenName == tokenExpected)
{
Connect(openToken, mToken);
Accept();
}
return(result);
}
/// <summary>
/// Parse ternary expression (a ? (b : c))
/// </summary>
SyntaxExpr ParseExprTernary()
{
SyntaxExpr result = ParseExprCompare();
// Or a ternary operator
if (mTokenName == "?")
{
Token q = Accept();
SyntaxExpr t1 = ParseExprTernary();
if (mTokenName != ":")
{
q.Reject("Matching ':' was not found");
return(Reject("Expecting a ':' to separate expression for the ternary '?' operator", REJECT_LINE));
}
result = new SyntaxExpr(q, result, new SyntaxExpr(Accept(), t1, ParseExprTernary()));
}
return(result);
}
/// <summary>
/// Parse an 'if' or 'elif' condition
/// </summary>
SyntaxExpr ParseIfCond()
{
// Parse condition
if (mTokenName != "(")
{
return(Reject("Expecting '('", REJECT_LINE));
}
Token open = Accept();
SyntaxExpr result = ParseExpr();
if (mTokenName != ")")
{
return(Reject("Expecting ')' - end of of expression", REJECT_LINE));
}
Connect(open, mToken);
Accept(")");
return(result);
}
/// <summary>
/// Read the open '(' or '[' parse the expression and connect
/// the ']' or ')'. Returns the expression that was parsed.
/// </summary>
SyntaxExpr ParseParen()
{
// Shouldn't ever happen
if (mTokenName != "(" && mTokenName != "[")
{
throw new Exception("Compiler error: Expecting '[' or '(' while parsing paren");
}
// Read open '(' or '[' and create an Expr
Token openToken = mToken;
string tokenExpected = openToken == "(" ? ")" : "]";
string [] rejectTokens = openToken == "(" ? REJECT_PAREN : REJECT_BRACKET;
Accept();
// Empty () or []?
if (mTokenName == tokenExpected)
{
// Return an empty () or []
Connect(openToken, mToken);
Reject("Expecting a parameter");
SyntaxExpr emptyExpr = new SyntaxExpr(Accept()); // Error, use ')' or ']'
return(emptyExpr);
}
// Parse all parameters (then add separator)
SyntaxExpr result = ParseExpr();
// If not ended properly, append a reject line
if (mTokenName != tokenExpected)
{
// The rest of the line is rejected
Reject("Expecting '" + tokenExpected + "'", rejectTokens);
}
if (mTokenName == tokenExpected)
{
Connect(openToken, mToken);
Accept();
}
return(result);
}
/// <summary>
/// Generate an expression list (as if this were lisp)
/// </summary>
void ToString(SyntaxExpr expr, StringBuilder sb, int level)
{
if (level >= 7)
{
sb.Append("*OVF*");
return;
}
if (Count == 0)
{
sb.Append(expr.mFunction);
return;
}
if (level != 0)
{
sb.Append("(");
}
if (expr.mFunction == "(")
{
sb.Append("'");
}
sb.Append(expr.mFunction);
if (expr.mFunction == "(")
{
sb.Append("'");
}
foreach (SyntaxExpr param in expr.mParameters)
{
sb.Append(", ");
ToString(param, sb, level + 1);
}
if (level != 0)
{
sb.Append(")");
}
}
/// <summary>
/// Rejects tokens until one of the stopTokens is found.
/// Marks at least one token with the error message.
/// </summary>
SyntaxExpr Reject(string errorMessage, string [] stopTokens)
{
// Mark all tokens to end of line with an error
Reject(errorMessage);
SyntaxExpr result = new SyntaxExpr(mToken);
// Skip the rest of this statement
while (true)
{
if (mTokenName == "")
{
return(result);
}
foreach (string token in stopTokens)
{
if (mTokenName == token)
{
return(result);
}
}
Accept();
}
}
/// <summary>
/// Evaluate a constant. If there is an error, the symbol
/// that caused it is rejected and the error bit is set.
/// </summary>
public static EvaluateConst Eval(SymbolTable symbols, SyntaxExpr expr)
{
if (expr == null)
{
return(new EvaluateConst());
}
if (expr.Count != 0)
{
expr.Function.Reject("Not yet supported");
return(new EvaluateConst());
}
if (expr.Function.Name.Length == 0)
{
return(new EvaluateConst());
}
// Parse number
if (char.IsDigit(expr.Function.Name[0]))
{
EvaluateConst result = new EvaluateConst();
result.Resolved = true;
// Attempt to scan hexadecimal value
if (expr.Function.Name.Length >= 3 &&
char.ToUpper(expr.Function.Name[1]) == 'X' &&
long.TryParse(expr.Function.Name.Substring(2),
NumberStyles.AllowHexSpecifier,
CultureInfo.CurrentCulture, out result.ValueInt))
{
result.WasHex = true;
return(result);
}
// Attempt to scan decimal value
if (long.TryParse(expr.Function.Name, out result.ValueInt))
{
return(result);
}
expr.Function.Reject("Error reading value");
return(new EvaluateConst());
}
// Parse identifier
if (expr.Function.Type == eTokenType.Identifier)
{
Symbol symbol = symbols.FindSymbol(expr.Function);
if (symbol == null)
{
expr.Function.Reject("Undefined symbol");
return(new EvaluateConst());
}
if (symbol.Decl.TypeName.Name != "int")
{
expr.Function.Reject("Constant value must be of type 'int'");
return(new EvaluateConst());
}
if (symbol.ResolvedName == "")
{
expr.Function.Reject("Unresolved symbol");
return(new EvaluateConst());
}
// We got the type, mark the symbol
expr.Function.AppendMessage(symbol.ResolvedName);
return(new EvaluateConst(symbol.ConstValue));
}
expr.Function.Reject("Unrecognized symbol in constant expression");
return(new EvaluateConst());
}
/// <summary>
/// Parse a single statement, which could be an expression.
/// Adds declaratins to the box locals.
/// NOTE: This can return NULL if there are no statements.
/// </summary>
public SyntaxExpr ParseStatement(SyntaxBox box, bool topLevel)
{
while (mTokenName == "else" || mTokenName == "elif")
{
Reject("This '" + mTokenName + "' is not inside an 'if' statement");
Accept();
}
// Check statement keywords first
bool needsSemicolon = true;
SyntaxExpr result = null;
if (mTokenName == "bit")
{
// Parse bit statement (optionally followed by assignment)
if (!topLevel)
{
Reject("'bit' declarations are only allowed at the top level");
}
result = ParseBitStatement(REJECT_LINE);
}
else if (mTokenName == "const")
{
// Parse const declaration
if (!topLevel)
{
Reject("'const' declarations are only allowed at the top level");
}
result = ParseConstStatement();
}
else if (mTokenName == "if")
{
// Parse if statement
needsSemicolon = false;
result = ParseIfStatement(box);
}
else
{
// Parse an expression
result = ParseExpr();
// Assignment statement?
if (mTokenName == "=")
{
// Generate an assignment statement
result = new SyntaxExpr(Accept(), result, ParseExpr());
}
}
// Ensure we have a valid statement
if (needsSemicolon && mTokenName != ";")
{
Reject("Expecting end of statement separator ';'", REJECT_LINE);
}
if (mTokenName == ";")
{
Accept();
}
return(result);
}
