[web-devel] Yesod 0.8 migration guide (release candidate?)

Yitzchak Gale gale at sefer.org
Thu Apr 21 16:27:53 CEST 2011

Michael Snoyman wrote:
> As a convenience, I'm considering exporting the following from the
> Yesod module:
>     mconcat (from Data.Monoid)
>     <> = mappend (from Data.Monoid)
>     Text (the strict version, from Data.Text)
> I know there was some talk a while ago of providing a <> operator in base,
> but I haven't heard anything about it since.

It may not have made it into base yet, but <> is defined in
Edward's semigroups package:


If you are going to export a <>, make sure it's that one to
avoid clashes. Even if you don't export <>, I think it's a good
idea to make every Monoid in Yesod a Semigroup instance.
And perhaps you'll also find some useful Semigroup instances
which aren't Monoids, or shouldn't be Monoids.


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