An environment can only bind a symbol to one expression, so the symbol "dog" in the tree environment is bound to an opaque reference to an environment (or machi

An environment can only bind a symbol to one expression, so the symbol "dog" in the tree environment is bound to an opaque reference to an environment (or machine), containing the dog's bindings. There can be many of these machines containing dog's bindings, but if you were to bind them all to dog, you would only have access to the most recently bound one, since binding a name in an environment overwrites any existing binding with a new one. The solution is therefore, that we must either use bindings such as "dog1", "dog2" and whatnot, or we have a binding "dogs" which binds a list of environment objects, which we can index to refer to a specific dog. Actually, "dogs" could itself just be an environment which binds specific dog's names, like spike to their respective environments ($define! dogs ($bindings->environment (spike ($spawn ...)) (charlie ($spawn ...)))) This might be less useful than a list though as there's no way to map over the dogs in an environment.