    "The string representation of the given [[integer]] in the
     base given by [[radix]]. If the given integer is negative,
     the string representation will begin with `-`. Digits
     consist of decimal digits `0` to `9`, together with and
     lowercase letters `a` to `z` for bases greater than 10.

     For example:

     - `formatInteger(-46)` is `\"-46\"`
     - `formatInteger(9,2)` is `\"1001\"`
     - `formatInteger(10,8)` is `\"12\"`
     - `formatInteger(511,16)` is `\"1ff\"`
     - `formatInteger(512,32)` is `\"g0\"`"
    throws (`class AssertionError`,
            "if [[radix]] is not between [[minRadix]] and
             [[maxRadix]]")
    see (`function parseInteger`)
    shared String formatInteger(
                "The integer value to format."
                Integer integer,
                "The base, between [[minRadix]] and [[maxRadix]]
                 inclusive."
                Integer radix = 10) {
        assert (minRadix <= radix <= maxRadix);
        if (integer == 0) {
            return "0";
        }
        variable {Character*} digits = {};
        variable Integer i = integer < 0
                             then integer
                             else -integer;
        while (i != 0) {
            Integer d = -(i % radix);
            Character c;
            if (0<=d<10) {
                c = (d+zeroInt).character;
            }
            else if (10<=d<36) {
                c = (d-10+aIntLower).character;
            }
            else {
                assert (false);
            }
            digits = digits.follow(c);
            i = (i + d) / radix;
        }
        if (integer < 0) {
            digits = digits.follow('-');
        }
        return String(digits);
    }