/* convert a decimal integer to a list of digits in base `base' */
dec2digits(d, base):= block([digits: []],
  while (d>0) do block([newdi: mod(d, base)],
    digits: cons(newdi, digits),
    d: round( (d - newdi) / base)),
  digits)$

dec2digits(123, 10);
/* [1, 2, 3] */
dec2digits(  8,  2);
/* [1, 0, 0, 0] */