See also http://pvp.haskell.org/faq

4.2.5.2

• Compatibility fix for base-4.12 which made accumArray stricter causing SHA-1's implementation to hang
• Modernize package description from the ancient cabal spec version 1.2 to version 2.2 and declare test executables as actual test-unit executables (and make them pass)
• Drop support for base < 4.3 (i.e. GHC < 7.0)
• Reduce dependency footprint of main library by dropping the dependecies on the test specific HUnit and QuickCheck libraries; these are now only depended upon by the actual test suites
• Reduce compile warnings

4.2.5.1

• Compatibility fix for base-4.6 (Bits class not implying Num anymore)

4.2.5

• Compatibility fix for base-4.5 (Num class not implying Show anymore)