F to_str(v)
   R ‘[ ’v.map(n -> hex(n).lowercase().zfill(2)).join(‘ ’)‘ ]’

F to_seq(UInt64 x)
   V i = 0
   L(ii) (9.<0).step(-1)
      I x [&] (UInt64(127) << ii * 7) != 0
         i = ii
         L.break

   [Byte] out
   L(j) 0 .. i
      out [+]= ((x >> ((i - j) * 7)) [&] 127) [|] 128

   out[i] (+)= 128
   R out

F from_seq(seq)
   UInt64 r = 0

   L(b) seq
      r = (r << 7) [|] (b [&] 127)

   R r

L(x) [UInt64(7'F), 40'00, 0, 003F'FFFE, 001F'FFFF, 0020'0000, 3311'A123'4DF3'1413]
   V s = to_seq(x)
   print(‘seq from ’hex(x).lowercase()‘ ’to_str(s)‘ back: ’hex(from_seq(s)).lowercase())