Re: [Haskell-cafe] containers license issue

12 Dec 2012

      Just for reference:

In Data/IntMap/Base.hs

highestBitMask :: Nat -> Nat
highestBitMask x0
  = case (x0 .|. shiftRL x0 1) of
     x1 -> case (x1 .|. shiftRL x1 2) of
      x2 -> case (x2 .|. shiftRL x2 4) of
       x3 -> case (x3 .|. shiftRL x3 8) of
        x4 -> case (x4 .|. shiftRL x4 16) of
#if !(defined(__GLASGOW_HASKELL__) && WORD_SIZE_IN_BITS==32)
         x5 -> case (x5 .|. shiftRL x5 32) of   -- for 64 bit platforms
#endif
          x6 -> (x6 `xor` (shiftRL x6 1))

In FXT bithigh.h:

static inline ulong highest_one(ulong x)
// Return word where only the highest bit in x is set.
// Return 0 if no bit is set.
{
#if defined  BITS_USE_ASM
    if ( 0==x )  return 0;
    x = asm_bsr(x);
    return  1UL<>1);
#endif  // BITS_USE_ASM
}

And in FXT bits/bithigh-edge.h:

static inline ulong highest_one_01edge(ulong x)
// Return word where all bits from (including) the
//   highest set bit to bit 0 are set.
// Return 0 if no bit is set.
//
// Feed the result into bit_count() to get
//   the index of the highest bit set.
{
#if defined  BITS_USE_ASM

    if ( 0==x )  return 0;
    x = asm_bsr(x);
    return  (2UL<>1;
    x |= x>>2;
    x |= x>>4;
    x |= x>>8;
    x |= x>>16;
#if  BITS_PER_LONG >= 64
    x |= x>>32;
#endif
    return  x;
#endif  // BITS_USE_ASM
}

=====

However... I think the easy solution for this is to just find this in
http://graphics.stanford.edu/~seander/bithacks.html, and cite it instead. I
looked briefly and couldn't find it, but I'm almost sure it's in there.

  - Clark

On Wed, Dec 12, 2012 at 11:37 AM, Niklas Larsson wrote:
...
2012/12/12 David Thomas :
...
Ah, that's more than we'd been told.  If that is the case, then
containers
is in violation of the GPL (unless they got permission to copy that code,
separately), and either must obtain such permission, be relicensed,
remove/replace that code.
I think it's just a confusion of language, the "derived" algorithm
clashes uncomfortably with the lawyerly "derived work". They are not
used in the same sense.
Niklas

Re: [Haskell-cafe] containers license issue

Clark Gaebel