get "libhdr"

let grayEncode(n) = n neqv (n >> 1)

let grayDecode(n) = grayDecodeStep(0, n)
and grayDecodeStep(r, n) =
    n = 0 -> r,
    grayDecodeStep(r neqv n, n >> 1)

let binfmt(n) =
    n = 0 -> 0,
    (n & 1) + 10 * binfmt(n >> 1)

let printRow(n) be
$(  let enc = grayEncode(n)
    let dec = grayDecode(enc)
    writef("%I2: %I5 => %I5 => %I5 => %I2*N",
           n, binfmt(n), binfmt(enc), binfmt(dec), dec)
$)

let start() be
    for i = 0 to 31 do printRow(i)