On 08-08-12 19:01, Simon Hengel wrote:

On Wed, Aug 08, 2012 at 12:22:39PM -0400, David Feuer wrote:

...

Changing scoping rules based on whether things are right next to each other? No thanks. Would expanding each let-less binding to a separate let "feel" more sound to you?

That was actually my first idea, but then two declarations at the same level will not be in the same binding group, so do x = y y = 1 would not compile. This would create a difference with all the other places where bindings may appear. However, having scope depend on things being next to each other (or rather, not having anything in between) is not new. Template Haskell declaration splices already cause separate binding groups for top-level declarations. Moreover, the new scope rule only holds for let-less bindings. If you use explicit lets nothing changes. -- Martijn

Hi, Martijn Schrage wrote:

...

Would expanding each let-less binding to a separate let "feel" more sound to you?

That was actually my first idea, but then two declarations at the same level will not be in the same binding group, so

do x = y y = 1

would not compile. This would create a difference with all the other places where bindings may appear.

But it would be in line with <- bindings in the do notation, so maybe it wouldn't feel so wrong. Tillmann

On 09-08-12 10:35, Tillmann Rendel wrote:

Hi,

Martijn Schrage wrote:

...

...

Would expanding each let-less binding to a separate let "feel" more sound to you?

That was actually my first idea, but then two declarations at the same level will not be in the same binding group, so

do x = y y = 1

would not compile. This would create a difference with all the other places where bindings may appear.

But it would be in line with <- bindings in the do notation, so maybe it wouldn't feel so wrong. It would absolutely be the easiest solution to implement, since as far as I can see, it requires only a small change to the parser. However, I still think it will be too confusing to have bindings that look the same as everywhere else but have different binding group rules. Especially since there is no reason for it from a semantic point of view (unlike when you mix in a monadic <- binding, after which it makes sense to have a new binding group.)

Anyhow, I'll submit it as a GHC feature request and see what happens. Cheers, Martijn Schrage -- Oblomov Systems (http://www.oblomov.com)

Tillmann

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