/// <summary>
/// Lookahead N
/// </summary>
/// <param name="index"></param>
/// <returns></returns>
protected Token Peek(int index = 0)
{
while (TokenBuf.Count <= index)
{
TokenBuf.Enqueue(NextToken());
}
Queue <Token> .Enumerator iter = TokenBuf.GetEnumerator();
for (int i = 0; i <= index; ++i)
{
iter.MoveNext();
}
return(iter.Current);
}
/// <summary>
/// types为空表示接受任何Token
/// </summary>
/// <param name="types"></param>
/// <returns></returns>
protected Token Consume(params TokenType[] types)
{
if (TokenBuf.Count == 0)
{
TokenBuf.Enqueue(NextToken());
}
if (types.Length != 0 && !Check(types))
{
Token t = TokenBuf.Dequeue();
StringBuilder sb = new StringBuilder("Expect ").Append(types[0].ToString());
for (int i = 1; i < types.Length; ++i)
{
sb.Append("/").Append(types[i].ToString());
}
throw new SyntaxError(sb.ToString(), t);
}
return(TokenBuf.Dequeue());
}
private Token NextToken()
{
Token ret;
if (FirstPass)
{
ret = Lexer.Next();
TokenBuf.Add(ret);
if (ret == Token.EOF)
{
FirstPass = false;
}
}
else
{
ret = TokenBuf[TokenBufIndex++];
}
return(ret);
}
