function Env(obj){
    var env = {}, outer = obj.outer || {};
    if (obj.parms.length != 0){
        for (var i = 0; i < obj.parms.length; i += 1)
             env[obj.parms[i]] = obj.args[i];
    }
    env.find = function(variable){
        if (variable in env)
            return env;
        else
            return outer.find(variable);
    };
    return env;
}