[math-fun] Bit Reversal Puzzle

For an unsigned 64-bit integer, define br(x) to be the "bit reversal" of x: bit positions 0 and 63 are swapped, 1 and 62 are swapped, and so on. What's the fastest way in generic C code to compute br(a) < br(b) [Don't spoil this if you've seen it already, please.] -tom -- -- http://cube20.org/ -- http://golly.sf.net/ --