relative-to—either :block or :current.
n—a real.
stream—an output stream designator. The default is standard output.
pprint-indent specifies the indentation to use in a logical block on stream.
If stream is a pretty printing stream
and the value of *print-pretty* is true,
pprint-indent sets the indentation in the innermost
dynamically enclosing logical block;
otherwise, pprint-indent has no effect.
N specifies the indentation in ems. If relative-to is :block, the indentation is set to the horizontal position of the first character in the dynamically current logical block plus n ems. If relative-to is :current, the indentation is set to the current output position plus n ems. (For robustness in the face of variable-width fonts, it is advisable to use :current with an n of zero whenever possible.)
N can be negative;
however, the total indentation cannot be moved
left of the beginning of the line
or left of the end of the rightmost per-line prefix—an attempt to move beyond
one of these limits is treated
the same as an attempt to move to that limit.
Changes in indentation caused by pprint-indent
do not take effect until after the next line break. In addition, in
miser mode all calls to pprint-indent are ignored, forcing the lines
corresponding to the logical block to line up under the first character in
the block.
An error is signaled if relative-to is any object other than :block or :current.