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Reverse the bits of an unsigned integer (UInt32)

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let reverse x =
    (* swap every neigbouring bit *)
    ((x &&& 0xAAAAAAAAu) >>> 1) ||| ((x &&& 0x55555555u) <<< 1)
    (* swap every 2 neighbouring bits *)
    |> fun x -> ((x &&& 0xCCCCCCCCu) >>> 2) ||| ((x &&& 0x33333333u) <<< 2)
    (* swap every 4 neighbouring bits *)
    |> fun x -> ((x &&& 0xF0F0F0F0u) >>> 4) ||| ((x &&& 0x0F0F0F0Fu) <<< 4)
    (* swap every 8 neighbouring bits *)
    |> fun x -> ((x &&& 0xFF00FF00u) >>> 8) ||| ((x &&& 0x00FF00FFu) <<< 8)
    (* and so forth, for say, 32 bit int *)
    |> fun x -> ((x &&& 0xFFFF0000u) >>> 16) ||| ((x &&& 0x0000FFFFu) <<< 16)
val reverse : x:uint32 -> uint32

Full name: Script.reverse
val x : uint32
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Link:http://fssnip.net/jU
Posted:12 years ago
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