It's a parallel list comprehension, as linked from the wiki page you referenced: https://downloads.haskell.org/ghc/9.4.4/docs/users_guide/exts/parallel_list_com

It's a parallel list comprehension, as linked from the wiki page you referenced: https://downloads.haskell.org/ghc/9.4.4/docs/users_guide/exts/parallel_list_comprehensions.html https://downloads.haskell.org/ghc/9.4.4/docs/users_guide/ext...