Calculator Lexer

calculator_lext.cs

// Lexer.cs
public class Lexer
{
    //...
    public Token NextToken()
    {
        //...
        char character = this.input[this.position];
        switch (character)
        {
                case '+':
                    token = new Token { Type = TokenType.PLUS, Literal = "+" };
                    break;
                case '-':
                    token = new Token { Type = TokenType.MINUS, Literal = "-" };
                    break;
                case '*':
                    token = new Token { Type = TokenType.MULTIPLY, Literal = "*" };
                    break;
               // ...
                default:
                    if(IsDigit(character))
                    {
                        token = new Token { Type = TokenType.INT };
                        token.Literal = this.ReadNumber();
                    }
                    else
                    {
                        token = new Token { Type = TokenType.ILLEGAL, Literal=""};
                    }
                    break;
            }
            this.position++;
            return token;
}