#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 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: #9231 -------------------------------------+------------------------------------ Changes (by hvr): * related: #9213 => #9231 Old description:
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
New description: As pointed out in #9231, the desired property "read . show ≡ id" is not satisfied for all resolutions. For instance, consider the following example: {{{#!hs
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#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler