Your example is parsing and you are essentially hiding the parse errors. Is Option not the absence of something? Wouldn’t a Result be a better fit here?
What’s the advantage over using with or changesets in this context?
cmo
dimitarvp
Having Option.new be used both for success and error is non-intuitive. For readability just have constructors for each variant: Option.some(value) and Option.none().
You are trying very hard to use for here for no good reason IMO. Having a with statement with several parsing / validation steps that returns Option.none() should any of them fail and only returns Option.some(year) if they all succeed is more readable, I believe.
Not to mention that you could eliminate most of your hand-rolled parsing code if you use nimble_parsec. 
I guess it all boils down to these questions: is the code supposed to be read by somebody else, ever? Is it only for your satisfaction and to exercise and gauge the validity of your idea? If so, then by all means, do continue. 
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Fl4m3Ph03n1x
The Option type is not meant to tell you about errors, it is meant to discard them.
A Result/Error Monad would be a better fit if you want o know exactly what failed and why.
If you are confused as to what these types are supposed to be, I recommend a series:
This example was always only focused on the Option type. Discussing the Result type is out of scope as I don’t have an implementation to make comparisons.
@dimitarvp Your opinion in the API has some merit. However, I decided the follow the same model as Witchcraft does, as I find it very user friendly. I guess it comes down to personal taste. If you invoke Option.new with a value, you get Some and if not, you get None. Alternatively, you can use the structs themselves as returns Option.Some... or Option.None. You have the choice if you want to go down that route. I just figured that a Option.new was simple enough.
In regards to your personal opinion in relation to the validity of this approach, we can have this discussion in another place (if you insist on having. I personally don’t).
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AstonJ
Please note some posts have been edited/removed to clean up the thread following OP’s request to remove the contentious part of their post.
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