class SymbolTable
{
public:
    SymbolTable() {}
    void insert(string variable, double value);
    double lookUp(string variable) const;
    void unusedVariableCheck();
private:
    struct Symbol
    {
        Symbol(string variable, double value, bool used)
        {
            this->variable = variable;
            this->value = value;
            this->used = used;
        }
        string variable;
        double value;
        bool used;
    };
    vector<Symbol> elements;
};