The reader might be inclined not to read the preface when starting with the book,
but rather at a later time when laziness or leisure leaves time for it. In the worst
case, the reader might come back to the preface angered by some lack of understanding
or, quite the opposite, angered by reading some undergraduate simplistic
explanations. By consulting the preface, the reader is asking the authors about their
goals in writing the book.
The main goal is declared by the book’s title, nevertheless with some restrictions
in mind.
The following publication is settled somewhere between a textbook and a computer
code manual. Its level is perhaps too specialized for a textbook and too broad
for a manual. A positive comment would be that its content includes rather practical
advice on what is usually described in a theoretical textbook, as well as presenting
in more detail the physical understanding of what the manual of a code
promises as a result. Dangling between these two extremes the authors could not
decide where to place the book exactly, so they decided to take the risk of sharing
the common ground in both.