Nathan Collins authored Dec 09, 2017 and Ben Gamari committed Jan 02, 2018

The example is using `join . atomically` to run IO actions computed by
STM transactions.

I couldn't figure out how to link to the STM docs in
`Control.Monad.STM`, because that module comes from the `stm` package,
not from `base`, even though `stm` is also part of the GHC source
tree. So, instead I linked to the STM docs in `GHC.Conc`, which seems
inferior to linking to `Control.Monad.STM`, but better than having no
links at all.