private static Token ScanDigits(StreamReaderExpanded reader)
{
string value = "";
TokenType type;
// Reads until it meets a symbol that isn't a digit.
while (Char.IsDigit(reader.PeekChar()))
{
value += reader.ReadChar();
}
// Checks whether the next symbol is a dot, if it isn't, the number is an integer.
if (reader.PeekChar() != '.')
{
type = TokenType.inum_token;
}
// If the next symbol was a dot the number is a float and we read the dot + a string of digits after.
else
{
type = TokenType.fnum_token;
value += reader.ReadChar();
// If there is no digits after the dot we throw an exception.
if (!Char.IsDigit(reader.PeekChar()))
{
throw new LexicalException(line);
}
// Reads the digits after the dot.
while (Char.IsDigit(reader.PeekChar()))
{
value += reader.ReadChar();
}
}
return(new Token(value, type, line));
}
private static void SkipComment(StreamReaderExpanded reader)
{
//Reads until the symbol right before the end of the line or file
while (reader.PeekChar() != '\n' && reader.Peek() > -1)
{
reader.Read();
}
}
private static Token TokenComp(StreamReaderExpanded reader, char expectedSymbol, TokenType option1, TokenType option2)
{
// Checks whether the symbol is the one expected.
if (reader.PeekChar() == expectedSymbol)
{
reader.Read();
return(new Token(option2, line));
}
// If it isn't the expected symbol and the options are the same it throws an exception.
// This could be if we expect && but only read &, then the second one would throw the exception.
else if (option1 == option2)
{
throw new LexicalException(line);
}
else
{
return(new Token(option1, line));
}
}
private static Token GetString(StreamReaderExpanded reader)
{
string value = "";
// Reads every character until it meets a new line symbol, or " symbol or EOF.
while (reader.PeekChar() != '\n' && reader.PeekChar() != '\"' && reader.Peek() > -1)
{
value += reader.ReadChar();
}
// Checks if the cause of the stopped while loop is a " symbol.
if (reader.PeekChar() == '\"')
{
reader.Read();
return(new Token(value, TokenType.stringval_token, line));
}
// Throw exception because of EOF or runaway string.
else
{
throw new LexicalException(line);
}
}
private static Token ScanWords(StreamReaderExpanded reader)
{
string value = "";
TokenType type;
// Reads all letters or digits until a nonletter and nondigit is read.
while (Char.IsLetterOrDigit(reader.PeekChar()))
{
value += reader.ReadChar();
}
/* Check for reserved keywords. In this case, only "true" and "false" are saved as values.
* Other values, such as "if" and "play", are always the same, and are therefore discarded to save space. */
if (Keywords.TryGetValue(value, out type))
{
return((type == TokenType.boolval_token) ? new Token(value, type, line) : new Token(type, line));
}
// Alternatively, the word is saved as an identifier token.
else
{
type = TokenType.id_token;
return(new Token(value, type, line));
}
}
public static Token Scan(StreamReaderExpanded reader)
{
Token ans = null;
// Advance if blank space
while (Char.IsWhiteSpace((char)reader.Peek()))
{
//Counts the line number for the exception message
if (reader.PeekChar() == '\n')
{
line += 1;
}
reader.Read();
}
// If end of file, return eof token
if (reader.EndOfStream)
{
ans = new Token(TokenType.eof_token, line);
}
else
{
// Scan digits
if (Char.IsDigit(reader.PeekChar()))
{
ans = ScanDigits(reader);
}
// Scan identifiers and keywords
else if (Char.IsLetter(reader.PeekChar()))
{
ans = ScanWords(reader);
}
else
{
char ch = reader.ReadChar();
switch (ch)
{
// Aritmetiske
case '+':
ans = new Token(TokenType.plus_token, line);
break;
case '-':
ans = new Token(TokenType.minus_token, line);
break;
case '=':
ans = TokenComp(reader, '=', TokenType.assign_token, TokenType.equal_token);
break;
case '*':
ans = new Token(TokenType.multiply_token, line);
break;
case '/':
ans = new Token(TokenType.divide_token, line);
break;
case '%':
ans = new Token(TokenType.modulo_token, line);
break;
case '^':
ans = new Token(TokenType.power_token, line);
break;
// Logiske
case '!':
ans = TokenComp(reader, '=', TokenType.not_token, TokenType.notequal_token);
break;
case '<':
ans = TokenComp(reader, '=', TokenType.lessthan_token, TokenType.lessorequal_token);
break;
case '>':
ans = TokenComp(reader, '=', TokenType.greaterthan_token, TokenType.greaterorequal_token);
break;
case '&':
ans = TokenComp(reader, '&', TokenType.and_token, TokenType.and_token);
break;
case '|':
ans = TokenComp(reader, '|', TokenType.or_token, TokenType.or_token);
break;
// Kontrolstruktur
case ';':
ans = new Token(TokenType.semicolon_token, line);
break;
case ',':
ans = new Token(TokenType.comma_token, line);
break;
// Datatyper
case '(':
ans = new Token(TokenType.lparen_token, line);
break;
case ')':
ans = new Token(TokenType.rparen_token, line);
break;
case '[':
ans = new Token(TokenType.lsbracket_token, line);
break;
case ']':
ans = new Token(TokenType.rsbracket_token, line);
break;
case '{':
ans = new Token(TokenType.lcbracket_token, line);
break;
case '}':
ans = new Token(TokenType.rcbracket_token, line);
break;
// Diverse
case '.':
ans = new Token(TokenType.dot_token, line);
break;
case ':':
ans = new Token(TokenType.colon_token, line);
break;
case '\"':
ans = GetString(reader);
break;
case '#':
SkipComment(reader);
break;
default:
throw new LexicalException(line);
}
}
}
return(ans);
}
