/// <summary>
/// Devuelve un valor entero que representa la prioridad de un token determinado.
/// </summary>
/// <param name="token"></param>
/// <returns></returns>
private static int GetTokenPriority(Token token)
{
if (token == null) return 10;
switch (token.Type)
{
case TokenType.Asterisk:
case TokenType.Slash:
case TokenType.Percent:
return 4;
case TokenType.Plus:
case TokenType.Minus:
return 3;
case TokenType.Equal:
case TokenType.NotEqual:
case TokenType.Greater:
case TokenType.GreaterEqual:
case TokenType.Less:
case TokenType.LessEqual:
return 2;
case TokenType.Ampersand:
case TokenType.Caret:
return 1;
case TokenType.Invalid:
return -1;
default:
return 0;
}
}
/// <summary>
/// Se mueve siempre que pueda al proximo token.
/// </summary>
/// <param name="c"></param>
/// <returns></returns>
public virtual void NextToken()
{
Token next = null;
if (HasMoreTokens())
{
char c = Read();
switch (c)
{
case '+':
next = new Token(TokenType.Plus, "+");
break;
case '-':
next = new Token(TokenType.Minus, "-");
break;
case '*':
next = new Token(TokenType.Asterisk, "*");
break;
case '/':
next = new Token(TokenType.Slash, "/");
break;
case '%':
next = new Token(TokenType.Percent, "%");
break;
case '&':
if (Peek() != '&')
next = new Token(TokenType.Invalid, c.ToString());
else
{
Read();
next = new Token(TokenType.Ampersand, "&&");
}
break;
case '|':
if (Peek() != '|')
next = new Token(TokenType.Invalid, c.ToString());
else
{
Read();
next = new Token(TokenType.Caret, "||");
}
break;
case '(':
next = new Token(TokenType.OpenedParenthesis, "(");
break;
case ')':
next = new Token(TokenType.ClosedParenthesis, ")");
break;
case '[':
next = new Token(TokenType.OpenedBracket, "[");
break;
case ']':
next = new Token(TokenType.ClosedBracket, "]");
break;
case '.':
next = new Token(TokenType.Dot, ".");
break;
case ',':
next = new Token(TokenType.Comma, ",");
break;
case '=':
if (Peek() == '=')
{
Read();
next = new Token(TokenType.Equal, "==");
}
else
next = new Token(TokenType.Assign, "=");
break;
case '!':
if (Peek() == '=')
{
Read();
next = new Token(TokenType.NotEqual, "!=");
}
else next = new Token(TokenType.Invalid, "!");
break;
case '>':
if (Peek() == '=')
{
Read();
next = new Token(TokenType.GreaterEqual, ">=");
}
else
next = new Token(TokenType.Greater, ">");
break;
case '<':
if (Peek() == '=')
{
Read();
next = new Token(TokenType.LessEqual, "<=");
}
else
next = new Token(TokenType.Less, "<");
break;
default:
if (char.IsLetter(c))
{
string nextValue = ReadWord(c);
if (nextValue == "true" || nextValue == "True")
next = new Token(TokenType.True, nextValue.ToLowerInvariant());
else if (nextValue == "false" || nextValue == "False")
next = new Token(TokenType.False, nextValue.ToLowerInvariant());
else
next = new Token(TokenType.Name, nextValue);
}
else if (char.IsDigit(c))
next = new Token(TokenType.Constant, ReadNumber(c));
break;
}
if (next == null)
next = new Token(TokenType.Invalid, c.ToString());
}
current = next;
}