As you know, Clon already provides seven built-in option types: flags
and six other types for valued options (see Built-In Valued Options). After using Clon for a while, you may find that however
brilliant and perfectly designed it is, none of the provided built-in
types fullfill your requirements exactly. There are two ways around
this: the right way and the wrong way (hint).
The wrong, although perhaps quicker way would be to use the
stropt option type to simply retrieve unprocessed string values,
and then do whatever tweaking required on them. In doing so, you risk
reinventing some of Clon’s wheels.
The right way is to define a new option type. Properly defined option
types are a good thing because they allow for reusability and also
extensibility, since new option types can always be defined on top of
others.
In this chapter we explain how to extend Clon by providing new option
types. We illustrate the process with the example of the built-in
enum one.
Oh, and I almost forgot. I hope it is obvious to everyone that new
option types are always valued. There’s no point in extending
Clon with options that don’t take any arguments, since we already
have flags.