public IEnumerator <Token> Scan(TextReader reader)
{
while (reader.Peek() != -1)
{
if (Char.IsWhiteSpace((char)reader.Peek()))
{
reader.Read();
}
else if (Char.IsDigit((char)reader.Peek()))
{
yield return(Token.FromDouble(ScanReal(reader)));
}
else
{
char c = (char)reader.Read();
switch (c)
{
case '+': yield return(Token.FromKind(Kind.Plus)); break;
case '-': yield return(Token.FromKind(Kind.Minus)); break;
case '*': yield return(Token.FromKind(Kind.Multiply)); break;
case '/': yield return(Token.FromKind(Kind.Divide)); break;
case '(': yield return(Token.FromKind(Kind.LeftParenthesis)); break;
case ')': yield return(Token.FromKind(Kind.RightParenthesis)); break;
default:
throw new ApplicationException("Illegal character: '" + c + "'");
}
}
}
yield return(Token.FromKind(Kind.EoF));
}
