public Token NextToken()
{
var tok = new Token();
skipWhitespace();
switch (ch)
{
case '=':
if (peekChar() == '=')
{
var ch = this.ch;
readChar();
tok = new Token(TokenType.EQUALS_EQUALS, $"{ch}{this.ch}");
}
else
{
tok = makeToken(TokenType.EQUALS);
}
break;
case '+':
tok = makeToken(TokenType.PLUS);
break;
case ';':
tok = makeToken(TokenType.SEMICOLON);
break;
case ',':
tok = makeToken(TokenType.COMMA);
break;
case '(':
tok = makeToken(TokenType.LPAREN);
break;
case ')':
tok = makeToken(TokenType.RPAREN);
break;
case '{':
tok = makeToken(TokenType.LBRACE);
break;
case '}':
tok = makeToken(TokenType.RBRACE);
break;
case '!':
if (peekChar() == '=')
{
var ch = this.ch;
readChar();
tok = new Token(TokenType.BANG_EQUALS, $"{ch}{this.ch}");
}
else
{
tok = makeToken(TokenType.BANG);
}
break;
case '-':
tok = makeToken(TokenType.MINUS);
break;
case '/':
tok = makeToken(TokenType.SLASH);
break;
case '*':
tok = makeToken(TokenType.ASTERISK);
break;
case '<':
tok = makeToken(TokenType.LT);
break;
case '>':
tok = makeToken(TokenType.GT);
break;
case '"':
tok.Type = TokenType.STRING;
tok.Literal = readString();
break;
case '[':
tok = makeToken(TokenType.LBRACKET);
break;
case ']':
tok = makeToken(TokenType.RBRACKET);
break;
case ':':
tok = makeToken(TokenType.COLON);
break;
case '\0':
tok.Literal = "";
tok.Type = TokenType.EOF;
break;
default:
if (ch.IsLetter())
{
tok.Literal = readIdentifier();
tok.Type = TokenFacts.LookupIdent(tok.Literal);
return(tok);
}
else if (ch.IsDigit())
{
tok.Literal = readNumber();
tok.Type = TokenType.INT;
return(tok);
}
else
{
tok = makeToken(TokenType.ILLEGAL);
}
break;
}
readChar();
return(tok);
}
