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Comment by cannam | Hacker News Reader

There must be some interesting reason why ".." and not the more common "..." - I wonder what?

No particular reason.

`..` and `...` both exist in the language, `..` is exclusive range and `...` is inclusive range. `..` is only in expressions right now, whereas `...` is only in patterns. Eventually, both will be available everywhere, possibly. At very least, `..` in patterns is getting added soon.

Since this is a pattern thing, probably `..` was chosen when `...` was the only range available in patterns, to distinguish this from that range pattern more. However, `..` will now be available in patterns, so its just historical.

(This is a longstanding feature, what's changed is just making it apply to more patterns.)

Reading through, they treat a range (like 1 .. 10 ) as pattern matching 1 2 3 4 5 6 7 8 9 10, with .. representing 2 3 4 5 6 7 8 9.

In that light, it actually makes sense.

Ah of course, that is quite widely used (e.g. Perl). If you already have that, I can see why you'd reuse the same token.

(edit: ok, I see from other replies that it's not that simple)

Minor correction, to match a range the syntax would be

  1 ... 10

I've seen the "..." used for matching a range of values, whereas ".." is used in other places where we disregard a value while patter matching.

I'm sure someone from the rust team can give a better answer, but to me this change looks like it was just bringing the pattern matching for structs to be consistent with other uses of ".."

Relevant RFC: https://github.com/rust-lang/rfcs/blob/master/text/1492-dotd...

It's less to type. The double period is already used for lots of other things in the language, so it feels like the correct choice.

They probably 'copied' Haskell here, which also uses "..".

Haskell doesn't have this feature though. I mean it does, but you can just leave out the ones you don't want matched, you don't have to put in any dots.

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