public Token Scan()
{
for (; ; Readch())
{
// line comments
if (m_Peek == '/' && m_Source[m_Current] == '/')
{
do
{
Readch();
} while (m_Peek != '\n');
}
// white spaces
if (m_Peek == ' ' || m_Peek == '\t' || m_Peek == '\r')
{
continue;
}
// new lines
if (m_Peek == '\n')
{
Line += 1;
}
else
{
break;
}
}
if (char.IsDigit(m_Peek))
{
int v = 0;
do
{
v = 10 * v + (m_Peek - '0');
Readch();
} while (char.IsDigit(m_Peek));
if (m_Peek != '.')
{
return(new Num(v));
}
float x = v;
float d = 10;
for (;;)
{
Readch();
if (!char.IsDigit(m_Peek))
{
break;
}
x = x + (m_Peek - '0') / d;
d = d * 10;
}
if (m_Peek == 'f')
{
Readch();
}
return(new Real(x));
}
else if (char.IsLetter(m_Peek))
{
StringBuilder b = new StringBuilder();
do
{
b.Append(m_Peek);
Readch();
} while (char.IsLetterOrDigit(m_Peek));
string s = b.ToString();
if (m_Words.ContainsKey(s))
{
return(m_Words[s]);
}
Word w = new Word(s, TagType.Id);
m_Words.Add(s, w);
return(w);
}
Token tok = new Token((int)m_Peek);
m_Peek = ' ';
return(tok);
}
private void Reserve(Word word)
{
m_Words.Add(word.Lexeme, word);
}