private bool ScanNumber()
{
bool is_number = false;
// this.Val = this.next_val_;
if (Char.IsNumber(input_sym_))
{
is_number = true;
this.Val = input_sym_ - '0';
Next();
}
while (Char.IsNumber(input_sym_))
{
is_number = true;
this.Val = 10 * this.Val + input_sym_ - '0';
Next();
}
if (is_number)
{
current_token_ = TokenHelper.Tokens.kNumber;
}
return(is_number);
}
public Scanner(string file_name) // opoen file and scan the first token into .input_sym_
{
identifier_table = new List <string>();
this.file_reader_ = new FileReader(file_name);
this.current_token_ = TokenHelper.Tokens.kNullToken;
Next();
GetSym();
}
public bool EatToken(TokenHelper.Tokens token_enum)
{
Next();
if (scanner_sym_ != token_enum)
{
Error("Expected " + Enum.GetName(typeof(TokenHelper.Tokens), token_enum));
return(false);
}
return(true);
}
private bool ScanIdentifier()
{
StringBuilder sb = new StringBuilder();
if (!Char.IsLetter(input_sym_))
{
return(false);
}
sb.Append(input_sym_);
Next();
while (Char.IsNumber(input_sym_) || (Char.IsLetter(input_sym_) && input_sym_ < (char)128))
{
sb.Append(input_sym_);
Next();
}
string token_str = sb.ToString();
// try to match with a keyword
if (TokenHelper.MatchKeyword(token_str, out current_token_))
{
return(true);
}
int pos = identifier_table.IndexOf(sb.ToString());
if (pos < 0)
{
pos = identifier_table.Count;
identifier_table.Add(sb.ToString());
}
// Id = next_id_;
Id = pos;
current_token_ = TokenHelper.Tokens.kIdent;
return(true);
}
public string Token2String(TokenHelper.Tokens token)
{
string key_str = TokenHelper.TOKENSET.FirstOrDefault(x => x.Value == token).Key;
return(key_str);
}
public TokenHelper.Tokens GetSym() // public int sym; // the current token on the input, 0 = error token, 255 = end-of-file token
{
TokenHelper.Tokens r = current_token_;
if (r == TokenHelper.Tokens.kEndofToken)
{
Next();
return(r);
}
if (!SkipSpace())
{
current_token_ = TokenHelper.Tokens.kEndofToken;
return(r);
}
if (input_sym_ == FileReader.kEndSymbol)
{
current_token_ = TokenHelper.Tokens.kEndofToken;
return(r);
}
if (ScanIdentifier() != false)
{
return(r);
}
if (ScanNumber() != false)
{
return(r);
}
switch (input_sym_)
{
case '/': {
Next();
if (input_sym_ == '/')
{
//Next();
file_reader_.SkipLine();
Next();
GetSym(); // OR: SkipCommentAndSpace
return(r);
}
else
{
current_token_ = TokenHelper.Tokens.kDivToken;
return(r);
}
break;
}
case '=': {
Next();
if (input_sym_ == '=')
{
Next();
current_token_ = TokenHelper.Tokens.kEqlToken;
return(r);
}
else
{
Error(@"'=' should be followed by '='");
current_token_ = TokenHelper.Tokens.kErrorToken;
return(r);
}
break;
}
case '!': {
Next();
if (input_sym_ == '=')
{
Next();
current_token_ = TokenHelper.Tokens.kNeqToken;
return(r);
}
else
{
Error(@"'!' should be followed by '='");
current_token_ = TokenHelper.Tokens.kErrorToken;
return(r);
}
break;
}
case '>': {
Next();
if (input_sym_ == '=')
{
Next();
current_token_ = TokenHelper.Tokens.kGeqToken;
return(r);
}
else
{
current_token_ = TokenHelper.Tokens.kGtrToken;
return(r);
}
break;
}
case '<': {
Next();
if (input_sym_ == '=')
{
Next();
current_token_ = TokenHelper.Tokens.kLeqToken;
return(r);
}
else if (input_sym_ == '-')
{
Next();
current_token_ = TokenHelper.Tokens.kBecomesToken;
return(r);
}
else
{
current_token_ = TokenHelper.Tokens.kIssToken;
return(r);
}
break;
}
case '+': {
Next();
current_token_ = TokenHelper.Tokens.kPlusToken;
return(r);
}
case '-': {
Next();
current_token_ = TokenHelper.Tokens.kMinusToken;
return(r);
}
case '*': {
Next();
current_token_ = TokenHelper.Tokens.kTimesTocken;
return(r);
}
case '.': {
Next();
current_token_ = TokenHelper.Tokens.kPeriodToken;
return(r);
}
case ',': {
Next();
current_token_ = TokenHelper.Tokens.kCommaToken;
return(r);
}
case ';': {
Next();
current_token_ = TokenHelper.Tokens.kSemiToken;
return(r);
}
case '(': {
Next();
current_token_ = TokenHelper.Tokens.kOpenparenToken;
return(r);
}
case ')': {
Next();
current_token_ = TokenHelper.Tokens.kCloseparenToken;
return(r);
}
case '[': {
Next();
current_token_ = TokenHelper.Tokens.kOpenbracketToken;
return(r);
}
case ']': {
Next();
current_token_ = TokenHelper.Tokens.kClosebracketToken;
return(r);
}
case '{': {
Next();
current_token_ = TokenHelper.Tokens.kBeginToken;
return(r);
}
case '}': {
Next();
current_token_ = TokenHelper.Tokens.kEndToken;
return(r);
}
}
{
current_token_ = TokenHelper.Tokens.kErrorToken;
}
return(r);
}
private void Next()
{
scanner_sym_ = scanner_.GetSym(); // advance to the next token
}
