private void MultiLineComment()
{
// we start inside a multi-line comment.
// but it could be nested
while ((Peek() == '*' && PeekNext() == '/') == false && !isAtEnd())
{
// Move through the body of the multi
if (Peek() == '\n')
{
Line++;
}
// We are already in a comment so eating chars is safe
// We start this method INSIDE the comment.
if (Match('/') && Match('*'))
{
MultiLineComment();
}
Advance();
}
if (isAtEnd())
{
CSLox.Error(this.Line, "Unterminated multi-line comment");
}
Advance(); Advance();
}
public Unit VisitVariableExpr(Expr.Variable expr)
{
if (_Scopes.Count != 0 && _Scopes[_Scopes.Count - 1].ContainsKey(expr.Name.Lexeme) &&
_Scopes[_Scopes.Count - 1][expr.Name.Lexeme] == false)
{
CSLox.Error(expr.Name, "Can't read local variable in it own initalizer.");
}
ResolveLocal(expr, expr.Name);
return(new Unit());
}
public void Interpret(Expr expression)
{
try
{
Object value = Evaluate(expression);
Console.WriteLine(Stringfy(value));
}
catch (RuntimeError ex)
{
CSLox.RuntimeError(ex);
}
}
private void Declare(Token name)
{
if (_Scopes.Count == 0)
{
return;
}
Dictionary <string, bool> scope = _Scopes[_Scopes.Count - 1];
if (scope.ContainsKey(name.Lexeme))
{
CSLox.Error(name, "Already a variabled with this name in this scope .");
}
scope.Add(name.Lexeme, false);
}
private void String()
{
while (Peek() != '"' && !isAtEnd())
{
if (Peek() == '\n')
{
Line++;
}
Advance();
}
if (isAtEnd())
{
CSLox.Error(Line, "Unterminated string");
return;
}
Advance();
// ignore the surrounding quotes!
var value = Source.Substring(Start + 1, (Current - 1) - (Start + 1));
AddToken(TokenType.STRING, value);
}
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.QUESTION); break;
case ':': AddToken(TokenType.SEMICOLON); 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 a line.
while (Peek() != '\n' && !isAtEnd())
{
Advance();
}
}
else if (Match('*'))
{
MultiLineComment();
}
else
{
AddToken(TokenType.SLASH);
}
break;
case ' ':
case '\r':
case '\t':
break; // ignoring whitespace and carry on.
case '\n':
this.Line++; // update the line, and carry on.
break;
case '"': String(); break;
default:
if (Char.IsDigit(c))
{
Number();
}
else if (IsAlpha(c))
{
Identifier();
}
else
{
CSLox.Error(this.Line, $"Unexpected Character '{c}'");
}
break;
}
}
private Exception Error(Token token, string message)
{
CSLox.Error(token, message);
return(new ParserError(message));
}
