Token.cs

using System;
using System.Collections.Generic;

namespace callculator
{
    public enum TokenType { None, Number, Function, FunctionArgSeparator, Operator, LeftParen, RightParen };

    public class Token
    {
        private static readonly Dictionary<string, TokenType> validTokens = new Dictionary<string, TokenType>() {
            {"^", TokenType.Operator},
            {"*", TokenType.Operator},
            {"/", TokenType.Operator},
            {"+", TokenType.Operator},
            {"-", TokenType.Operator},
            {"#", TokenType.Operator},
            {"@", TokenType.Operator},
            {"(", TokenType.LeftParen},
            {")", TokenType.RightParen},
            {",", TokenType.FunctionArgSeparator},
            {"sin", TokenType.Function},
            {"cos", TokenType.Function},
            {"tan", TokenType.Function},
            {"abs", TokenType.Function},
            {"max", TokenType.Function},
            {"min", TokenType.Function},
            {"neg", TokenType.Function},
            {"avg", TokenType.Function},
            {"sqrt", TokenType.Function},
            {"vavg", TokenType.Function}
        };

        TokenType type;
        string value;

        public TokenType Type
        {
            get
            {
                return type;
            }
        }

        public String Value
        {
            get
            {
                return value;
            }
        }

        public Token(string value)
        {
            this.value = value;
            this.type = GetTokenType();
        }

        private TokenType GetTokenType()
        {
            TokenType tokenType;
            if (!validTokens.TryGetValue(this.value, out tokenType))
            {
                // TODO may not actually be a number.
                tokenType = TokenType.Number;
            }

            return tokenType;
        }
    }
}