In that hypothetical context, the field name wouldn't be usable as a function—at least without future Dependent Haskell. On Mon, Sep 20, 2021, 1:19 PM Tom Ellis < tom-lists-haskell-cafe-2017@jaguarpaw.co.uk> wrote:

On Mon, Sep 20, 2021 at 01:13:43PM -0400, David Feuer wrote:

...

Does one field name for one datatype always refer to a field with the same type? Or is there some wacky extension that would allow things like

data Foo = Bar { zoom :: Int } | Baz { zoom :: Char }

I'm hoping I don't have to worry about the latter possibility....

Me too! Under such circumstances what would the type of field-as-function be? _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

I was just looking for confirmation. I'm playing around with using generics to make field-based lenses and traversals, and I don't want any unpleasant surprises. On Mon, Sep 20, 2021, 1:43 PM Brandon Allbery wrote:

Well, there is already an extension that turns off selector-as-function, although I don't recall the name off the top of my head. I am not sure there's a way to access such fields as this at all if you use it, since e.g. HasField probably doesn't let you do types by constructor name.

On Mon, Sep 20, 2021 at 1:21 PM David Feuer wrote:

...

In that hypothetical context, the field name wouldn't be usable as a function—at least without future Dependent Haskell.

On Mon, Sep 20, 2021, 1:19 PM Tom Ellis < tom-lists-haskell-cafe-2017@jaguarpaw.co.uk> wrote:

...

On Mon, Sep 20, 2021 at 01:13:43PM -0400, David Feuer wrote:

...

Does one field name for one datatype always refer to a field with the same type? Or is there some wacky extension that would allow things like

data Foo = Bar { zoom :: Int } | Baz { zoom :: Char }

I'm hoping I don't have to worry about the latter possibility....

Me too! Under such circumstances what would the type of field-as-function be? _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

_______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- brandon s allbery kf8nh allbery.b@gmail.com