// constructs a token with a string literal
private string MakeString(int startIndex)
{
while (Peek() != '"' && !IsAtEnd())
{
if (Peek() == '\n')
{
line++;
}
Advance();
}
// Unterminated string.
if (IsAtEnd())
{
Basil.Error(line, "Unterminated string.");
return("");
}
// The closing ".
Advance();
// Trim the surrounding quotes.
string value = source.Substring(startIndex, (current) - (startIndex + 1));
return(value);
}
// constructs a token with a string literal
private void MakeString()
{
while (Peek() != '"' && !IsAtEnd())
{
if (Peek() == '\n')
{
line++;
}
Advance();
}
// Unterminated string.
if (IsAtEnd())
{
Basil.Error(line, "Unterminated string.");
return;
}
// The closing ".
Advance();
// Trim the surrounding quotes.
string value = source.Substring(start + 1, (current - 1) - (start + 1));
AddToken(Token.TokenType.String, value);
}
public object VisitVariableExpr(Expr.Variable expr)
{
if (scopes.Count != 0 && scopes.Peek().ContainsKey(expr.name.lexeme) && scopes.Peek()[expr.name.lexeme] == false)
{
Basil.Error(expr.name, "Cannot read local variable in its own initializer.");
}
ResolveLocal(expr, expr.name);
return(null);
}
public object VisitThisExpr(Expr.This expr)
{
if (currentClass == ClassType.None)
{
Basil.Error(expr.Keyword, "Cannot use 'this' outside of a class.");
return(null);
}
ResolveLocal(expr, expr.Keyword);
return(null);
}
private void Declare(Token name)
{
if (scopes.Count == 0)
{
return;
}
if (scopes.Peek().ContainsKey(name.lexeme))
{
Basil.Error(name, "Variable with this name is already declared in this scope.");
}
scopes.Peek()[name.lexeme] = false;
}
public object VisitSuperExpr(Expr.Super expr)
{
if (currentClass == ClassType.None)
{
Basil.Error(expr.Keyword, "Cannot use 'super' outside of a class.");
}
else if (currentClass != ClassType.Subclass)
{
Basil.Error(expr.Keyword, "Cannot use 'super' in a class with no superclass.");
}
ResolveLocal(expr, expr.Keyword);
return(null);
}
public void Interpret(List <Stmt> statements)
{
try
{
// statements be empty?
foreach (Stmt statement in statements)
{
Execute(statement);
}
}
catch (RuntimeError error)
{
Basil.RuntimeError(error);
}
}
public object VisitReturnStmt(Stmt.Return stmt)
{
if (currentFunction == FunctionType.None)
{
Basil.Error(stmt.keyword, "Cannot return from top level code.");
}
if (stmt.value != null)
{
if (currentFunction == FunctionType.Initializer)
{
Basil.Error(stmt.keyword, "Cannot return a value from an initializer.");
}
Resolve(stmt.value);
}
return(null);
}
private void ImportToken(int tokenStart)
{
//var c = peek();
while (IsWhiteSpace(Peek()))
{
//c = peek();
Advance();
}
if (Peek() != '"')
{
Basil.Error(line, "Unexpected character.");
return;
}
else
{
Advance();
string path = MakeString(current);
// import
if (!imports.Contains(path))
{
imports.Add(path);
// scrub preprocessing from code
var tokenLength = current - tokenStart;
source = source.Remove(tokenStart, tokenLength);
current -= tokenLength;
string newSource = System.IO.File.ReadAllText(path);
Importer importer = new Importer(newSource);
string preprocessedNewSource = importer.Process();
source = source.Insert(current, preprocessedNewSource);
current += preprocessedNewSource.Length + 1;
}
else
{
// scrub preprocessing from code
source = source.Remove(tokenStart, current - tokenStart);
}
}
}
// scan an individual token
private void ScanToken()
{
char c = Advance();
switch (c)
{
// Single-character
case '(': AddToken(Token.TokenType.LeftParenthesis); break;
case ')': AddToken(Token.TokenType.RightParenthesis); break;
case '{': AddToken(Token.TokenType.LeftBrace); break;
case '}': AddToken(Token.TokenType.RightBrace); break;
//case '[': addToken(Token.TokenType.LeftBracket); break;
//case ']': addToken(Token.TokenType.RightBracket); break;
case ',': AddToken(Token.TokenType.Comma); break;
case '.': AddToken(Token.TokenType.Dot); break;
//case '-': AddToken(Token.TokenType.Minus); break;
//case '+': AddToken(Token.TokenType.Plus); break;
case ';': AddToken(Token.TokenType.Semicolon); break;
//case '*': AddToken(Token.TokenType.Star); break;
//case '%': AddToken(Token.TokenType.Percent); break;
case '-':
if (Match('-'))
{
AddToken(Token.TokenType.MinusMinus);
}
else if (Match('='))
{
AddToken(Token.TokenType.MinusEqual);
}
else
{
AddToken(Token.TokenType.Minus);
}
break;
case '+':
if (Match('+'))
{
AddToken(Token.TokenType.PlusPlus);
}
else if (Match('='))
{
AddToken(Token.TokenType.PlusEqual);
}
else
{
AddToken(Token.TokenType.Plus);
}
break;
case '*': AddToken(Match('=') ? Token.TokenType.StarEqual : Token.TokenType.Minus); break;
case '%': AddToken(Match('=') ? Token.TokenType.PercentEqual : Token.TokenType.Minus); break;
//case '?': addToken(Token.TokenType.If); break;
//case '|': addToken(Token.TokenType.Else); break;
// Single or double characters
case '!': AddToken(Match('=') ? Token.TokenType.BangEqual : Token.TokenType.Bang); break;
case '=': AddToken(Match('=') ? Token.TokenType.EqualEqual : Token.TokenType.Equal); break;
case '<': AddToken(Match('=') ? Token.TokenType.LessEqual : Token.TokenType.Less); break;
case '>': AddToken(Match('=') ? Token.TokenType.GreaterEqual : Token.TokenType.Greater); break;
case '/':
if (Match('/'))
{
// A comment goes until the end of the line.
while (Peek() != '\n' && !IsAtEnd())
{
Advance();
}
}
else if (Match('*'))
{
// A comment goes until the end of the block
while (!IsAtEnd())
{
if (Peek() == '*' && PeekNext() == '/')
{
Advance();
Advance();
break;
}
Advance();
}
}
else if (Match('='))
{
AddToken(Token.TokenType.SlashEqual);
}
else
{
AddToken(Token.TokenType.Slash);
}
break;
// Literals
case '"': MakeString(); break;
// White-space
case ' ':
case '\r':
case '\t':
// Ignore whitespace.
break;
case '\n':
line++;
break;
// if not a language token, determine what the user has entered and if it is valid
default:
if (IsDigit(c))
{
MakeNumber();
}
else if (IsAlpha(c))
{
Identifier();
}
else
{
Basil.Error(line, "Unexpected character.");
}
break;
}
}
// reports an error about a token
private ParseError Error(Token token, string message)
{
Basil.Error(token, message);
return(new ParseError());
}
private Expr Assignment()
{
Expr expr = Or();
if (Match(Token.TokenType.PlusPlus))
{
Token variable = Previous();
if (expr is Expr.Variable v)
{
Token name = v.name;
return(new Expr.Assign(name,
new Expr.Binary(expr, new Token(Token.TokenType.Plus, "+", null, variable.line), new Expr.Literal(1.0))));
}
else if (expr is Expr.Get)
{
Expr.Get get = (Expr.Get)expr;
return(new Expr.Set(get.Objekt, get.Name, new Expr.Binary(expr, new Token(Token.TokenType.Plus, "+", null, variable.line), new Expr.Literal(1.0))));
}
Error(variable, "Invalid assignment target.");
}
if (Match(Token.TokenType.MinusMinus))
{
Token variable = Previous();
if (expr is Expr.Variable v)
{
Token name = v.name;
return(new Expr.Assign(name,
new Expr.Binary(expr, new Token(Token.TokenType.Plus, "+", null, variable.line), new Expr.Literal(-1.0))));
}
else if (expr is Expr.Get)
{
Expr.Get get = (Expr.Get)expr;
return(new Expr.Set(get.Objekt, get.Name, new Expr.Binary(expr, new Token(Token.TokenType.Plus, "+", null, variable.line), new Expr.Literal(-1.0))));
}
Error(variable, "Invalid assignment target.");
}
if (Match(Token.TokenType.Equal, Token.TokenType.MinusEqual, Token.TokenType.PlusEqual,
Token.TokenType.StarEqual, Token.TokenType.SlashEqual, Token.TokenType.PercentEqual,
Token.TokenType.PlusPlus))
{
Token equals = Previous();
Expr tempValue = Assignment();
Expr assignedValue = tempValue;
switch (equals.type)
{
case Token.TokenType.Equal: break;
case Token.TokenType.MinusEqual:
assignedValue = new Expr.Binary(expr, new Token(Token.TokenType.Minus, "-", null, equals.line), tempValue);
break;
case Token.TokenType.PlusEqual:
assignedValue = new Expr.Binary(expr, new Token(Token.TokenType.Plus, "+", null, equals.line), tempValue);
break;
case Token.TokenType.StarEqual:
assignedValue = new Expr.Binary(expr, new Token(Token.TokenType.Star, "*", null, equals.line), tempValue);
break;
case Token.TokenType.SlashEqual:
assignedValue = new Expr.Binary(expr, new Token(Token.TokenType.Slash, "/", null, equals.line), tempValue);
break;
case Token.TokenType.PercentEqual:
assignedValue = new Expr.Binary(expr, new Token(Token.TokenType.Percent, "%", null, equals.line), tempValue);
break;
default: Basil.Error(Previous().line, "Tried to create assignment statement but tokens were invalid.");
break;
}
if (expr is Expr.Variable v)
{
Token name = v.name;
return(new Expr.Assign(name, assignedValue));
}
else if (expr is Expr.Get)
{
Expr.Get get = (Expr.Get)expr;
return(new Expr.Set(get.Objekt, get.Name, assignedValue));
}
Error(equals, "Invalid assignment target.");
}
//else if (Match(Token.TokenType.MinusEqual))
//{
// Token equals = Previous();
// Expr value = Assignment();
// // replace assignment expression with (expr - value)
// Expr minusEquals = new Expr.Binary(expr, new Token(Token.TokenType.Minus, "-", null, equals.line), value);
// if (expr is Expr.Variable v)
// {
// Token name = v.name;
// return new Expr.Assign(name, minusEquals);
// }
// else if (expr is Expr.Get)
// {
// Expr.Get get = (Expr.Get)expr;
// return new Expr.Set(get.Objekt, get.Name, minusEquals);
// }
// Error(equals, "Invalid assignment target.");
//}
return(expr);
}
