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Comment by bsaul | Hacker News Reader

I'm thinking pretty much the opposite regarding fragility and growing your system. The fact that adding a case in the enum have the compiler tells you all the places your programm needs to handle the case is a tremendous bonus !

The problem is that we're not talking about the same things. You're talking about making new things behave the way the an existing interface wanted, and i'm talking about a data structure updating.

Once again, interface is not data..

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> the compiler tells you all the places your programm needs to handle the case is a tremendous bonus

Except this is simply not true if you have any wildcard patterns in any of your matches. Besides, it's easy to grep for one or each of the names of the types in your closed sum. Which is what you're going to do anyway if you have any wild card patterns!

> interface is not data

I don't know what you intend to communicate by saying this.

"this is not true if.." Well, yes indeed, you can ignore features of a language, but i don't see how it prooves any point. As for the grep, i really have no idea what you're talking about ( maybe advanced pattern matching features of advanced language ?). I'm really talking about something very basic, like what swift is doing.

My point about interface vs data is that those are two different things, and that i don't think you can't try to solve an issue on type compositions with a feature working on functions only.

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