func[] fwddiff s[] n .
   for i to n
      for j = 1 to len s[] - 1
         s[j] = s[j + 1] - s[j]
      .
      len s[] -1
   .
   return s[]
.
s[] = [ 90 47 58 29 22 32 55 5 55 73 ]
print fwddiff s[] 1
print fwddiff s[] 2
print fwddiff s[] 9