#15081: Finite list becomes infinite after maping fractional function for high numbers -------------------------------------+------------------------------------- Reporter: Onsed | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.2.2 Keywords: | Operating System: Linux Architecture: x86_64 | Type of failure: Incorrect result (amd64) | at runtime Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Tested with version 8.2.2 and 8.0.2 (stack lts-11.5, lts-9.21, nightly-2018-04-14) with GHC and GHCi on archlinux amd64. **Code that produces wrong results** {{{ map (/2) [9007199254740990..9007199254740991] }}} **Expected behaviour** same as with low values: {{{ map (/2) [5..6] }}} resulting in: {{{ [2.5,3.0] }}} **Actual behaviour** resulting in an infinite list: {{{ [4.503599627370495e15,4.5035996273704955e15,4.503599627370496e15..] }}} **Similar code that produces expected results** multiplication works: {{{ map (*2) [9007199254740990..9007199254740991] }}} slightly smaller number work: {{{ map (/2) [9007199254740989..9007199254740990] }}} using a comma to produce the same list works: {{{ map (/2) [9007199254740990,9007199254740991] }}} **Similar code that also produces unexpected results** more elements in the list: {{{ map (/2) [9007199254740990..9007199254740999] map (/2) [9007199254740990..9007199354740999] }}} substituting the number and doing calculations: {{{ map (/2) [9007199254740990..9007199254740990+1] let a = 9007199254740990 map (/2) [a..a+1] }}} using scan and fold: {{{ foldl1 (/) [9007199254740990..9007199254740991] scanl1 (/) [9007199254740990..9007199254740991] }}} **Notes** This somehow only happens with high numbers when using fractional operations and using .. to construct the list. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15081 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler