I think most people find that Union Types are a wonderfull thing. I would 
argue that much of the beauty of Union Types comes from using them in a 
case-of statement, having the compiler complain when there is a case one 
haven't covered.

Strings and numbers are not so wonderfull, because they span essentially 
unlimited values, so case-of statements become less valuable.

However, strings and numbers still need to be used in production apps for 
several reasons:
1) Union Types is not supported in Json, so one needs to convert to/from 
strings or numbers for communicating with other systems.
2) Union Types are not comparable, and so cannot be used as keys in Sets or 

So a server might send me some json where the current user language is 
represented by an Int (0  and 1, norwegian and english) and the current 
game being played is a string ("chess", "checkers", "reversi"). It would be 
great to have some compiler help for these values (say, you forgot the case 
statement for "reversi"), AND it would be great to avoid writing 
encoders/decoders for the union types and converting back and forth several 

Enums would help with this.

The way I imagine this to work is that an enum essentially represents a 
restricted set of String or Number. Once the compiler sees that you're 
working with an enum, it could help you out in case statements. And since 
an enum is just a string, or just a number, they can be used in the same 
places where one would normally use them, like as a value in a select.

One would need a way to check that a string/number matches the values of an 
enum though. Something like `Enum.matches : MyStringEnum -> Maybe (Enum 

The one thing I can think of which makes this a bad addition to Elm, is 
that it might be a bit confusing for beginners when to use enum and when to 
use unions... maybe.

Anyway, what do people think of this?

You received this message because you are subscribed to the Google Groups "Elm 
Discuss" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to elm-discuss+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

Reply via email to