#16340: Improve properFraction for Ratio -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: (none) Type: task | Status: new Priority: normal | Milestone: 8.10.1 Component: Core | Version: 8.6.3 Libraries | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Runtime Unknown/Multiple | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- We define {{{#!hs properFraction (x:%y) = (fromInteger (toInteger q), r:%y) where (q, r) = quotRem x y }}} The first problem is that this produces a lazy pair. The second problem is that it uses `fromInteger . toInteger` rather than `fromIntegral`; the latter has rewrite rules that the former lacks. The whole thing should be written as {{{#!hs properFraction (x:%y) = (q', r:%y) where !(q, r) = quotRem x y !q' = fromIntegral q }}} or possibly {{{#!hs properFraction (x:%y) = (fromIntegral q, r:%y) where !(q, r) = quotRem x y }}} The latter is better if someone only wants the fractional part and is using `Integral` types for which `fromIntegral` is unusually expensive, but I don't know if that's really worth worrying about. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16340 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler