Nicolas Cellier uploaded a new version of Collections to project The Trunk:
http://source.squeak.org/trunk/Collections-nice.248.mcz

==================== Summary ====================

Name: Collections-nice.248
Author: nice
Time: 10 December 2009, 6:09:40 am
UUID: 5d63293d-c113-c84e-8437-2fed14a79a58
Ancestors: Collections-nice.247

Just for fun, optimize a bit more WideCharacterSet bitmap:do:
1) it now enumerates Characters in ascending value
2) the trick to eliminate the lowest bit is just beautiful (a generalization of isPowerOfTwo)
Of course, I could also tabulate all the bits in an Array of 255 ByteArray, but that would be no fun...

=============== Diff against Collections-nice.247 ===============

Item was changed:
  ----- Method: WideCharacterSet>>bitmap:do: (in category 'private') -----
  bitmap: aMap do: aBlock
  	"Execute a block with each value (0 based) corresponding to set bits.
  	Implementation: this version works best for sparse maps.
  	The powers of two and highBit tables are inlined for speed"
  	
+ 	| byte byteOffset lowBits |
+ 	lowBits := #[1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 6 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 7 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 6 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 8 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 6 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 7 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 6 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1 5 1 2 1 3 1 2 1 4 1 2 1 3 1 2 1]. "The lowBits table is a 1-based bitOffset"
- 	| byte bitOffset byteOffset powersOf2 highBits |
- 	powersOf2 := #[1 2 4 8 16 32 64 128].
- 	highBits := #[0 1 1 2 2 2 2 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7].
  	1 to: aMap size do: [:i | 
  		(byte := aMap at: i) = 0 ifFalse: [
+ 			byteOffset := (i bitShift: 3) - 9. "This byteOffset is -1 based"
+ 			["Evaluate the block with 0-based (byteOffset + bitOffset)"
+ 			aBlock value: (byteOffset + (lowBits at: byte)).
+ 			"Eliminate the low bit and loop if some bit remain"
+ 			(byte := byte bitAnd: byte - 1) = 0] whileFalse]]!
- 			byteOffset := (i - 1) bitShift: 3.
- 			[aBlock value: (byteOffset + (bitOffset := highBits at: byte)).
- 			(byte := byte - (powersOf2 at: 1 + bitOffset)) = 0] whileFalse]]!