An arg, any object,
is printed without escape characters
(as by princ). If arg is a string,
its characters
will be output verbatim.
If arg is nil it will be printed as nil;
the colon modifier (~:A) will cause an arg of nil to be printed as (),
but if arg is a composite structure, such as a list or vector,
any contained occurrences of nil will still be printed as nil.
~mincolA inserts spaces on the right, if necessary, to make the
width at least mincol columns. The @
modifier causes the spaces
to be inserted on the left rather than the right.
~mincol,colinc,minpad,padcharA
is the full form of ~A,
which allows control of the padding.
The string is padded on the right (or on the left if the
@ modifier is used) with at least minpad copies
of padchar; padding characters are then inserted colinc characters
at a time until the total width is at least mincol.
The defaults are 0 for mincol and minpad, 1 for colinc,
and the space character for padchar.
~A binds *print-escape* to false,
and *print-readably* to false.