#9240: "read . show ≡ id" not satisfied by Data.Fixed ------------------------------------+------------------------------------- Reporter: hvr | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: libraries/base | Version: 7.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #9213 | ------------------------------------+------------------------------------- As pointed out in #9213, the desired property "read . show ≡ id" is not satisfied for all resolutions. For instance, consider the following example: {{{
data B7 instance HasResolution B7 where resolution _ = 128
1.070 :: Fixed B7 1.062 1.062 :: Fixed B7 1.054
read "1.070" :: Fixed B7 1.062 read "1.062" :: Fixed B7 1.054 }}}
This behaviour can be reproduced all the way back to GHC 7.2.1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9240 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler