F encode_neg_base(=n, b)
   I n == 0
      R ‘0’
   [Int] out
   L n != 0
      (n, V rem) = divmod(n, b)
      I rem < 0
         n++
         rem -= b
      out.append(rem)
   R reversed(out).map(String).join(‘’)

F decode_neg_base(nstr, b)
   I nstr == ‘0’
      R 0
   V total = 0
   L(ch) reversed(nstr)
      V i = L.index
      total += Int(ch) * b ^ i
   R total

print(‘Encode 10 as negabinary (expect 11110)’)
V result = encode_neg_base(10, -2)
print(result)
I decode_neg_base(result, -2) == 10
   print(‘Converted back to decimal’)
E
   print(‘Error converting back to decimal’)
print(‘Encode 146 as negaternary (expect 21102)’)
result = encode_neg_base(146, -3)
print(result)
I decode_neg_base(result, -3) == 146
   print(‘Converted back to decimal’)
E
   print(‘Error converting back to decimal’)
print(‘Encode 15 as negadecimal (expect 195)’)
result = encode_neg_base(15, -10)
print(result)
I decode_neg_base(result, -10) == 15
   print(‘Converted back to decimal’)
E
   print(‘Error converting back to decimal’)