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Later I discovered that by default GHC rejected almost all my report-conforming (H98 and H2010) code.

Do you mean that GHC can't compile Haskell2010 conformant code? Can you please post (or point to) some examples?

This page [1] lists the ways in which GHC diverges from the standard.

Erik

[1] https://downloads.haskell.org/~ghc/master/users-guide/bugs.html

The main problem was that my code relied on constraint (Num a) implying (Eq a) per the standard. I also had context clauses in data declarations. Thus I had to make pervasive, albeit trivial, changes to get past GHC's nonconformance. (Presumably option -XHaskell2010 would have papered over the trouble, but I prefer to maximize code portability.) Doug McIlroy