#14818: Provide highestOneBit function in Data.Bits module -------------------------------------+------------------------------------- Reporter: kostmo | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: | Version: 8.2.2 libraries/base | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- This function yields the [https://stackoverflow.com/a/17379704/105137 largest power of 2 less than or equal to the given number]. Relative to the Java standard library, which [https://docs.oracle.com/javase/7/docs/api/java/lang/Integer.html#highestOneB...) provides this function], there is a gap in the Haskell library, even though the Haskell docs [https://hackage.haskell.org/package/base-4.10.1.0/docs/Data- Bits.html#v:countLeadingZeros describe a method to calculate logBase2 via the `countLeadingZeros` function]. From the Java documentation:
The implementations of the "bit twiddling" methods (such as `highestOneBit` and `numberOfTrailingZeros`) are based on material from Henry S. Warren, Jr.'s ''Hacker's Delight'', (Addison Wesley, 2002).
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14818 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler