[mc10]

The AgeMin/AgeMax example seems more of a deficiency due to a lack of named function parameters; it would be equally clear if it had a type signature (using OCaml as an example) of

    val is_admissible : min_age:int -> max_age:int -> bool

[exceptione]

There are other places were you use types as well.

Also, if you later decide that an Age should not be int, but a string, you wont miss it in refactoring whereas in your example you don't have that facility.