This is a module for doing integer arithmetic in arbitrary base
representations.  A representation, or "flex", is determined by
what symbols you use for +, -, and the digits.  The base that
you are working in is the number of digits you use to represent
your numbers.  Given a flex it can do the following:

  o Convert string representations of numbers to a convenient
    internal form for calculations as needed.

  o Convert from one internal representation to another,
    transparently changing bases as required.

  o Write the internal representation back to a string.

  o Handle large integer arithmetic.

A sample use would be to write 128 bit MD5 hashes using whatever
set of characters you want.