private void LexString()
{
while (Peek() != '"' && !IsAtEnd())
{
if (Peek() == '\n')
{
line++;
}
Advance();
}
// Unterminated string.
if (IsAtEnd())
{
VenaError.LexicalError(line, "Unterminated string.");
return;
}
// The closing ".
Advance();
// Trim the surrounding quotes.
String value = source.Substring(start + 1, (current - 1) - (start + 1));
AddToken(TokenType.STRING, value);
}
public bool Define(Token name, VType type)
{
if (!Values.TryAdd(name.Lexeme, type))
{
string definedType = Enum.GetName(typeof(VType), Values[name.Lexeme]);
VenaError.ParseError(name, $"Variable '{name.Lexeme}' already defined with type '{definedType}'.");
return(false);
}
return(true);
}
public bool ValidAssignment(Token name, VType assignType)
{
// Check to see if the token has already been defined.
if (!Values.ContainsKey(name.Lexeme))
{
VenaError.ParseError(name, $"Undefined variable '{name.Lexeme}'.");
return(false);
}
// Check to see if the defined token matches the assignee type.
if (Values[name.Lexeme] == assignType)
{
return(true);
}
VenaError.ParseError(name,
$"Assigning type '{Enum.GetName(typeof(VType), assignType)}' to already defined type '{Enum.GetName(typeof(VType), Values[name.Lexeme])}'.");
return(false);
}
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.PERCENT); 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;
// Comments
case '/':
if (Match('/'))
{
// A comment goes until the end of the line.
while (Peek() != '\n' && !IsAtEnd())
{
Advance();
}
}
else
{
AddToken(TokenType.SLASH);
}
break;
// Ignore whitespace.
case ' ':
case '\r':
case '\t':
break;
case '\n':
if (column == 2)
{
AddToken(TokenType.NEW_LINE);
}
line++;
column = 0;
break;
// Strings
case '"': LexString(); break;
default:
if (IsDigit(c))
{
Number();
}
else if (IsAlpha(c))
{
Identifier();
}
else
{
VenaError.LexicalError(line, "Unexpected character.");
}
break;
}
}
ParseError Error(Token token, String message)
{
VenaError.ParseError(token, message);
return(new ParseError());
}
