public void TestTokenClass()
{
var tok_c = new Token('c');
Assert.AreEqual('c', tok_c.TagValue);
Assert.AreEqual("c", tok_c.ToString());
var tok_9 = new Token('9');
Assert.AreEqual('9', tok_9.TagValue);
Assert.AreEqual("9", tok_9.ToString());
}
/// <summary>
/// Read and return the current token
/// </summary>
/// <returns></returns>
public Token Scan()
{
//for white spaces
for (; !this.EofReached; this.ReadChar())
{
if (_curr == ' ' || _curr == '\t')
{
continue;
}
else if (_curr == '\r')
{
this.ReadChar(); //eat \r
++Line;
}
else break;
}
if (this.EofReached) return null;
//for operators like && !=, etc
switch (_curr)
{
case '&':
return this.ReadChar('&') ? Word.and : new Token('&');
case '|':
return this.ReadChar('|') ? Word.or : new Token('|');
case '=':
return this.ReadChar('=') ? Word.eq : new Token('=');
case '!':
return this.ReadChar('=') ? Word.ne : new Token('!');
case '<':
return this.ReadChar('=') ? Word.le : new Token('<');
case '>':
return this.ReadChar('=') ? Word.ge : new Token('>');
}
//for numbers
if (char.IsDigit(_curr))
{
int v = 0;
do{
v = 10 * v + (int)(_curr - '0');
this.ReadChar();
} while (char.IsDigit(_curr));
if (_curr != '.') return new Num(v);
float f = v;
for (float d = 10; ; d *= 10)
{
this.ReadChar();
if (!char.IsDigit(_curr)) break;
f += (int)(_curr - 48) / d;
}
return new Real(f);
}
//for identifiers
if (char.IsLetter(_curr))
{
var b = new StringBuilder();
do
{
b.Append(_curr);
this.ReadChar();
} while (char.IsLetterOrDigit(_curr));
var s = b.ToString();
if (KeyWords.ContainsKey(s)) return KeyWords[s];
else return KeyWords[s] = new Word(s, Tag.ID);
}
//for the rest
var tok = new Token(_curr);
if (!this.EofReached) _curr = ' ';
return tok;
}
public void AddIdentifier(Token tok, Id id)
{
this.SymbolTable.Add(tok, id);
}
public Id Get(Token tok)
{
for(var e = this; e != null; e = e.Prev)
if (e.SymbolTable.ContainsKey(tok)) return e.SymbolTable[tok];
return null;
}
/// <summary>
/// Recognize next token and save in _look;
/// </summary>
public void Move()
{
_look = _lexer.Scan();
}