#9564: Floating point subnormals overrounded on output -------------------------------------+------------------------------------- Reporter: jrp | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Runtime | Version: 7.8.3 System | Keywords: Resolution: | Architecture: x86_64 (amd64) Operating System: MacOS X | Difficulty: Unknown Type of failure: Incorrect | Blocked By: result at runtime | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by jrp): For the record, looking through the code, libraries/base/GHC/Float.lhs seems to use {{{FloatToDigits}}} to generate the decimal representation. The algorithm used is "based on" "Printing Floating-Point Numbers Quickly and Accurately"-- by R.G. Burger and R.K. Dybvig in PLDI 96. http://www.cs.indiana.edu/~dyb/pubs /FP-Printing-PLDI96.pdf This version uses a much slower logarithm estimator. It should be improved. In turn, that algorithm was based on "How to Print Floating-Point Numbers Accurately" by Steele and White http://kurtstephens.com/files/p372-steele.pdf but it does not distinguish between significand and insignifican trailing zeros. The latest approach to conversion appears to be "Printing Floating-Point Numbers Quickly and Accurately with Integers" by Florian Loitsch http://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf (Bryan O'Sullivan http://www.serpentine.com/blog/2011/06/29/here-be- dragons-advances-in-problems-you-didnt-even-know-you-had/ has provided a library for the Double version http://hackage.haskell.org/package/double- conversion.) For a full set of references, including to source code, see http://www.ryanjuckett.com/programming/printing-floating-point-numbers/ I'll have a further think about this, including rwbarton's comments. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9564#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler