// output of ./demo/bits/debruijn-lookup-demo.cc:
// Description:
//% Determination of the lowest bit in a word via De Bruijn sequences.
db=...1.111
dbt[k]=
0 1 2 3 4 5 6 7
0 1 2 4 7 3 6 5
Lowest bit == 0:
x = .......1
db * x = ...1.111
shifted = ........ == 0
==> lookup = 0
Lowest bit == 1:
x = ......1.
db * x = ..1.111.
shifted = .......1 == 1
==> lookup = 1
Lowest bit == 2:
x = .....1..
db * x = .1.111..
shifted = ......1. == 2
==> lookup = 2
Lowest bit == 3:
x = ....1...
db * x = 1.111...
shifted = .....1.1 == 5
==> lookup = 3
Lowest bit == 4:
x = ...1....
db * x = .111....
shifted = ......11 == 3
==> lookup = 4
Lowest bit == 5:
x = ..1.....
db * x = 111.....
shifted = .....111 == 7
==> lookup = 5
Lowest bit == 6:
x = .1......
db * x = 11......
shifted = .....11. == 6
==> lookup = 6
Lowest bit == 7:
x = 1.......
db * x = 1.......
shifted = .....1.. == 4
==> lookup = 7