private void MultilineComment()
{
// A /* comment goes until it hits the closing */
while (!IsAtEnd())
{
if (Peek() == '\n')
{
line++;
}
// Check for comment end.
if (Peek() == '*')
{
Advance();
if (Peek() == '/' && !IsAtEnd())
{
Advance();
return;
}
}
else
{
Advance();
}
}
if (IsAtEnd())
{
CsLox.Error(line, "Unterminated comment.");
}
}
private void String()
{
while (Peek() != '"' && !IsAtEnd())
{
if (Peek() == '\n')
{
line++;
}
Advance();
}
// Unterminated string.
if (IsAtEnd())
{
CsLox.Error(line, "Unterminated string.");
return;
}
// The closing ".
Advance();
// Trim the surrounding quotes.
string value = source.Substring(start + 1, current - (start + 2));
AddToken(TokenType.STRING, value);
}
public object VisitBreakStmt(Break stmt)
{
if (currentLoop == LoopType.NONE)
{
CsLox.Error(stmt.Keyword, "Break statement must be inside a loop.");
}
return(null);
}
public object VisitThisExpr(This expr)
{
if (currentClass == ClassType.NONE)
{
CsLox.Error(expr.Keyword, "Cannot use 'this' outside of a class.");
}
ResolveLocal(expr, expr.Keyword);
return(null);
}
public void Interpret(List <Stmt> statements)
{
try
{
foreach (Stmt statement in statements)
{
Execute(statement);
}
}
catch (RuntimeException re)
{
CsLox.RuntimeError(re);
}
}
public object VisitVariableExpr(Variable expr)
{
if (scopes.Count > 0 && scopes.Peek().TryGetValue(expr.Name.Lexeme, out bool value))
{
if (!value)
{
CsLox.Error(expr.Name, "Cannot read local variable in its own initializer.");
}
}
ResolveLocal(expr, expr.Name);
return(null);
}
public object VisitSuperExpr(Super expr)
{
if (currentClass == ClassType.NONE)
{
CsLox.Error(expr.Keyword, "Cannot use 'super' outside of a class.");
}
else if (currentClass != ClassType.SUBCLASS)
{
CsLox.Error(expr.Keyword, "Cannot use 'super' in a class with no superclass.");
}
ResolveLocal(expr, expr.Keyword);
return(null);
}
private void Declare(Token name)
{
if (scopes.Count == 0)
{
return;
}
Dictionary <string, bool> scope = scopes.Peek();
if (scope.ContainsKey(name.Lexeme))
{
CsLox.Error(name, "Variable with this name already declared in this scope.");
}
scope[name.Lexeme] = false;
}
public object VisitClassStmt(Class stmt)
{
ClassType enclosingClass = currentClass;
currentClass = ClassType.CLASS;
Declare(stmt.Name);
Define(stmt.Name);
if (stmt.Superclass != null && stmt.Name.Lexeme.Equals(stmt.Superclass.Name.Lexeme))
{
CsLox.Error(stmt.Superclass.Name, "A class cannot inherit from itself.");
}
if (stmt.Superclass != null)
{
currentClass = ClassType.SUBCLASS;
Resolve(stmt.Superclass);
BeginScope();
scopes.Peek()["super"] = true;
}
BeginScope();
scopes.Peek()["this"] = true;
foreach (Function method in stmt.Methods)
{
FunctionType declaration = FunctionType.METHOD;
if (method.Name.Lexeme.Equals("init"))
{
declaration = FunctionType.INITIALIZER;
}
ResolveFunction(method, declaration);
}
EndScope();
if (stmt.Superclass != null)
{
EndScope();
}
currentClass = enclosingClass;
return(null);
}
public object VisitReturnStmt(Return stmt)
{
if (currentFunction == FunctionType.NONE)
{
CsLox.Error(stmt.Keyword, "Cannot return from top-level code.");
}
if (stmt.Value != null)
{
if (currentFunction == FunctionType.INITIALIZER)
{
CsLox.Error(stmt.Keyword, "Cannot return a value from an initializer.");
}
Resolve(stmt.Value);
}
return(null);
}
private ParseException Error(Token token, string message)
{
CsLox.Error(token, message);
return(new ParseException());
}
private void ScanToken()
{
char c = Advance();
switch (c)
{
case '(':
AddToken(TokenType.LEFT_PAREN);
break;
case ')':
AddToken(TokenType.RIGHT_PAREN);
break;
case '{':
AddToken(TokenType.LEFT_BRACE);
break;
case '}':
AddToken(TokenType.RIGHT_BRACE);
break;
case ',':
AddToken(TokenType.COMMA);
break;
case '.':
AddToken(TokenType.DOT);
break;
case '-':
AddToken(TokenType.MINUS);
break;
case '+':
AddToken(TokenType.PLUS);
break;
case ';':
AddToken(TokenType.SEMICOLON);
break;
case '*':
AddToken(TokenType.STAR);
break;
case '?':
AddToken(TokenType.QUERY);
break;
case ':':
AddToken(TokenType.COLON);
break;
case '!':
AddToken(Match('=') ? TokenType.BANG_EQUAL : TokenType.BANG);
break;
case '=':
AddToken(Match('=') ? TokenType.EQUAL_EQUAL : TokenType.EQUAL);
break;
case '<':
AddToken(Match('=') ? TokenType.LESS_EQUAL : TokenType.LESS);
break;
case '>':
AddToken(Match('=') ? TokenType.GREATER_EQUAL : TokenType.GREATER);
break;
case '/':
if (Match('/'))
{
// A comment goes until the end of the line.
while (Peek() != '\n' && !IsAtEnd())
{
Advance();
}
}
else if (Match('*'))
{
MultilineComment();
}
else
{
AddToken(TokenType.SLASH);
}
break;
case '%':
AddToken(TokenType.PERCENT);
break;
case ' ':
case '\r':
case '\t':
// Ignore whitespace.
break;
case '\n':
line++;
break;
case '"':
String();
break;
default:
if (IsDigit(c))
{
Number();
}
else if (IsAlpha(c))
{
Identifier();
}
else
{
CsLox.Error(line, "Unexpected character.");
}
break;
}
}