#14377: some results not expected with the addition -------------------------------------+------------------------------------- Reporter: vanto | Owner: (none) Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by svenpanne): * status: new => closed * resolution: => invalid Comment: I fully understand that you want to change the standard way of `Show`ing `Double`s, but this won't happen: There is an informal understanding that `read` and `show` are a (weak) kind of inverses: {{{ #!haskell almostIdentity x = read (show x) `asTypeOf` x }}} There is no formal requirement in the Haskell Report for this, but you can be sure that lots of code out there would break for no good reason if the standard `Show` instance would simply lower the precision. Improving the implementation so that it would output as few characters as possible while retaining precision ''and'' performance would be another story, as has already been pointed out. Again: If you want some special formatting, use e.g.: {{{ Prelude> Text.Printf.printf "%.5g\n" 12.3456789 12.34568 }}} Just for the record: Try the equivalent of your examples in Chrome's JavaScript console, in Firefox, Python 3.6's IDLE, in DrRacket's console etc. etc., and you will see the same results as in GHC(i), and for a good reason. Another thing: A bug tracker is not really the right place to discuss wild new ideas, IRC e.g. might be a better place to get some initial feedback and perhaps learn why things are done they way they are. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14377#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler