Re: [GHC] #9810: encodeFloat 1 2047 = -1024.0

#9810: encodeFloat 1 2047 = -1024.0 -------------------------------------+------------------------------------- Reporter: luite | Owner: hvr Type: bug | Status: patch Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.9 Resolution: | Keywords: ieee Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: #9811 Test Case: | Blocking: | Differential Revisions: Phab:D486 | -------------------------------------+------------------------------------- Comment (by Herbert Valerio Riedel ): In [changeset:"e2af452cd533778c5447719c59429d72bb1fe00d/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="e2af452cd533778c5447719c59429d72bb1fe00d" Restore exact old semantics of `decodeFloat` `integer-gmp2` uses the new 64bit-based IEEE deconstructing primop introduced in b62bd5ecf3be421778e4835010b6b334e95c5a56. However, the returned values differ for exceptional IEEE values: Previous (expected) semantics:

decodeFloat (-1/0) (-4503599627370496,972)

decodeFloat (1/0) (4503599627370496,972)

decodeFloat (0/0) (-6755399441055744,972)

Currently (broken) semantics:

decodeFloat (-1/0 :: Double) (-9223372036854775808,-53)

decodeFloat (1/0 :: Double) (-9223372036854775808,-53)

decodeFloat (0/0 :: Double) (-9223372036854775808,-53)

This patch reverts to the old expected semantics. I plan to revisit the implementation during GHC 7.11 development. This should address #9810 Reviewed By: austin, ekmett, luite Differential Revision: https://phabricator.haskell.org/D486 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9810#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler