However, that’s not a very satisfying way of looking at the output. You can write a dump-db function that dumps out the database in a more human-readable format, like this:

    1. TITLE:    Home
    2. ARTIST:   Dixie Chicks
    3. RATING:   9
    4. RIPPED:   T
    6. TITLE:    Fly
    7. RATING:   8
    8. RIPPED:   T
    10. TITLE:    Roses
    11. ARTIST:   Kathy Mattea
    12. RATING:   7

    The function looks like this:

    This function works by looping over all the elements of *db* with the **DOLIST** macro, binding each element to the variable cd in turn. For each value of cd, you use the function to print it.

    The second argument to **FORMAT** is a format string that can contain both literal text and directives telling **FORMAT** things such as how to interpolate the rest of its arguments. Format directives start with ~ (much the way printf‘s directives start with %). **FORMAT** understands dozens of directives, each with their own set of options.3 However, for now I’ll just focus on the ones you need to write dump-db.

    The ~a directive is the aesthetic directive; it means to consume one argument and output it in a human-readable form. This will render keywords without the leading : and strings without quotation marks. For instance:

    1. CL-USER> (format t "~a" "Dixie Chicks")
    2. Dixie Chicks
    3. NIL

    or:

    1. CL-USER> (format t "~a:~10t~a" :artist "Dixie Chicks")
    2. ARTIST:   Dixie Chicks
    3. NIL

    Now things get slightly more complicated. When **FORMAT** sees ~{ the next argument to be consumed must be a list. **FORMAT** loops over that list, processing the directives between the ~{ and ~}, consuming as many elements of the list as needed each time through the list. In dump-db, the **FORMAT** loop will consume one keyword and one value from the list each time through the loop. The ~% directive doesn’t consume any arguments but tells **FORMAT** to emit a newline. Then after the ~} ends the loop, the last ~% tells **FORMAT** to emit one more newline to put a blank line between each CD.

    Technically, you could have also used **FORMAT** to loop over the database itself, turning our dump-db function into a one-liner.

    That’s either very cool or very scary depending on your point of view.