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();
}
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;
}
}
public Unit VisitThisExpr(Expr.This expr)
{
if (this.CurrentClass == ClassType.NONE)
{
CSLox.Error(expr.Keyword,
"Can't use 'this' outside of a class.");
return(new Unit());
}
ResolveLocal(expr, expr.Keyword);
return(new Unit());
}
public Unit VisitReturnStmt(Stmt.Return stmt)
{
if (CurrentFunction == FunctionType.NONE)
{
CSLox.Error(stmt.Keyword, "Can't return from top-level code");
}
if (stmt.Value != null)
{
Resolve(stmt.Value);
}
return(new Unit());
}
public Unit VisitVariableExpr(Expr.Variable expr)
{
if (Scopes.Count != 0)
{
var scope = Scopes.Peek();
if (scope.ContainsKey(expr.Name.Lexeme) && scope[expr.Name.Lexeme] == false)
{
CSLox.Error(expr.Name, "Can't read local variable in it's own initalizer");
}
}
ResolveLocal(expr, expr.Name);
return(new Unit());
}
public Unit VisitSuperExpr(Expr.Super expr)
{
if (CurrentClass == ClassType.NONE)
{
CSLox.Error(expr.Keyword, "Can't use 'super' outside of a class.");
}
else if (CurrentClass != ClassType.SUBCLASS)
{
CSLox.Error(expr.Keyword, "Can't use 'super' in a class with no superclass");
}
ResolveLocal(expr, expr.Keyword);
return(new Unit());
}
public Unit VisitVariableExpr(Expr.Variable expr)
{
if (Scopes.Count != 0)
{
var scope = Scopes.Peek();
if (scope.ContainsKey(expr.Name.Lexeme) && scope[expr.Name.Lexeme] == false)
{
CSLox.Error(expr.Name, "Can't read local variable in it's own initalizer");
}
}
// Where a variable is referenced
// we send that info into to the interpreter
ResolveLocal(expr, expr.Name);
return(new Unit());
}
public Unit VisitClassStmt(Stmt.Class stmt)
{
ClassType enclosingClass = this.CurrentClass;
CurrentClass = ClassType.CLASS;
Declare(stmt.Name);
Define(stmt.Name);
if (stmt.SuperClass != null && stmt.Name.Lexeme == stmt.SuperClass.Name.Lexeme)
{
CSLox.Error(stmt.SuperClass.Name, "A class can't inherit from itself.");
}
/// Resolver doesn't resolve Global variables and that environment. (Where most inheritence will occur.)
/// Lox allows delcaraions inside of existing blocks, and as they are variable must be resolved.
if (stmt.SuperClass != null)
{
CurrentClass = ClassType.SUBCLASS;
Resolve(stmt.SuperClass);
}
if (stmt.SuperClass != null)
{
BeginScope();
Scopes.Peek().Add("super", true);
}
BeginScope();
Scopes.Peek().Add("this", true);
foreach (Stmt.Function method in stmt.Methods)
{
FunctionType declaration = FunctionType.METHOD;
if (method.Name.Lexeme.Equals("init"))
{
declaration = FunctionType.INITIALISER;
}
ResolveFunction(method, declaration);
}
EndScope();
if (stmt.SuperClass != null)
{
EndScope();
}
this.CurrentClass = enclosingClass;
return(new Unit());
}
private void Declare(Token name)
{
if (Scopes.Count == 0)
{
return;
}
var scope = Scopes.Peek();
if (scope.ContainsKey(name.Lexeme))
{
CSLox.Error(name, "Already a variable with this name in this scope.");
}
else
{
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);
}
public Unit VisitReturnStmt(Stmt.Return stmt)
{
if (CurrentFunction == FunctionType.NONE)
{
CSLox.Error(stmt.Keyword, "Can't return from top-level code");
}
if (stmt.Value != null)
{
// Small hack to stop 'erberts return from a constructor.
// Terminates current instancec
if (CurrentFunction == FunctionType.INITIALISER)
{
CSLox.Error(stmt.Keyword, "Can't return a value from an initialiser.");
}
Resolve(stmt.Value);
}
return(new Unit());
}
private void NaiveMultiLineComment(int nested = 1)
{
// we start inside a multi-line comment.
// but it could be nested
while (!isAtEnd())
{
// Move through the body of the multi
if (Peek() == '\n')
{
Line++;
}
if (Peek() == '*' && PeekNext() == '/')
{
Advance();
break;
}
if (Peek() == '/' && PeekNext() == '*')
{
Advance(); Advance();
NaiveMultiLineComment(nested + 1);
}
// Annoying this cannot be done until the end.
// We have not checked the current char
Advance();
}
if (isAtEnd())
{
CSLox.Error(this.Line, "Unterminated multi-line comment");
}
else
{
// Here we are at the end of the multi line comment
// munch the last char.
Advance();
}
}
/// <summary>
/// A string has been started "
/// this collects all the characters until the end.
/// </summary>
private void StringSequence()
{
// Move until we reach the end of a string;
while (Peek() != '"' && !isAtEnd())
{
if (Peek() == '\n')
{
Line++;
}
Advance();
}
if (isAtEnd())
{
CSLox.Error(Line, "Unterminated string");
return;
}
// Move past the final "
Advance();
// ignore the surrounding quotes, and create the token
var value = Source.Substring(Start + 1, (Current - 1) - (Start + 1));
AddToken(STRING, value);
}
private Exception Error(Token token, string message)
{
CSLox.Error(token, message);
return(new ParserError(message));
}
private void ScanToken()
{
char c = Advance();
switch (c)
{
case '(': AddToken(LEFT_PAREN); break;
case ')': AddToken(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(Match('=') ? BANG_EQUAL : BANG); break;
case '=': AddToken(Match('=') ? EQUAL_EQUAL : EQUAL); break;
case '<': AddToken(Match('=') ? LESS_EQUAL : LESS); break;
case '>': AddToken(Match('=') ? GREATER_EQUAL : GREATER); break;
case '/':
if (Match('/'))
{
// A comment goes until the end of a line.
while (Peek() != '\n' && !isAtEnd())
{
Advance();
}
}
else if (Match('*'))
{
NaiveMultiLineComment();
}
else
{
AddToken(SLASH);
}
break;
case ' ':
case '\r':
case '\t':
break; // ignoring whitespace and carry on.
case '\n':
this.Line++; // update the line nunber, and carry on.
break;
case '"': StringSequence(); break;
// Capturing all Numbers is simpler than 1 case per number.
case char val when(Char.IsDigit(val)): Number(); break;
// Capturing all a-Z AND _
case char val when IsAlpha(val): Identifier(); break;
default:
CSLox.Error(this.Line, "Unexpected Character");
break;
}
}
