#9231: 7.8 regression in Read instance of Data.Fixed.Pico -------------------------------------+------------------------------------ Reporter: leonbaum2 | Owner: Type: bug | Status: new Priority: highest | Milestone: 7.8.3 Component: libraries/base | Version: 7.8.2 Resolution: | Keywords: regression Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by Herbert Valerio Riedel <hvr@…>): In [changeset:"c1035d51edaac2f388a0630e2ad25391e7e3c1ab/ghc"]: {{{ #!CommitTicketReference repository="ghc" revision="c1035d51edaac2f388a0630e2ad25391e7e3c1ab" Fix regression in Data.Fixed Read instance (re #9231) `convertFixed` operates under the wrong assumption that `Data.Fixed.resolution` returns a base-10 exponent `e`, whereas it actually returns the power-of-10 value `10^e`. So while the code (that was introduced in 5f19f951d8 / #7483) happens to compute a correct result by coincidence, it allocates huge integer values in the process (i.e. `10^(10^e)`) which cause long computations which eventually result in out-of-memory conditions for `e`-values beyond `Data.Fixed.Milli`. A proper long-term fix would probably be to extend the `HasResolution` type-class to have a 2nd method providing the `e` value. Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org> Differential Revision: https://phabricator.haskell.org/D25 }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9231#comment:7> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler