There are many smaller examples of OS projects in Haskell, but for better examples of production systems you only have to look to areas requiring high assurance such as finance, where a number of large companies use Haskell and other functional languages. (BoA, Barclays, Credit Suisse, Standard Chartered, etc.)
It's true that there a lot of Haskell blogs focused on research level Category theory, but the concepts there don't need to be used or understood for high quality, production ready code. I'm actually not a Haskell guy, and very much of the mindset that you should use the right tool for the job, but being dismissive of languages with unique features such as being lazy by default is shortsighted.
The Haskell community is smaller than others but there are numerous highquality projects, including kernel/OS level projects that you don't mention:
HaLVM, Haskell Unikernels - https://github.com/GaloisInc/HaLVM
The specification model of the sel4 microkernel - https://github.com/seL4/l4v/tree/master/spec/haskell
There are many smaller examples of OS projects in Haskell, but for better examples of production systems you only have to look to areas requiring high assurance such as finance, where a number of large companies use Haskell and other functional languages. (BoA, Barclays, Credit Suisse, Standard Chartered, etc.)
It's true that there a lot of Haskell blogs focused on research level Category theory, but the concepts there don't need to be used or understood for high quality, production ready code. I'm actually not a Haskell guy, and very much of the mindset that you should use the right tool for the job, but being dismissive of languages with unique features such as being lazy by default is shortsighted.