Specify the indentation to use in the current logical block if stream, which defaults to *standard-output*, is a pretty-printing stream and *print-pretty* is true, otherwise do nothing. See pprint-logical-block. n is the indention to use, in ems, the width of an ``m'', and relative-to can be either:

:block

Indent relative to the column the current logical blockstarted on.

:current

Indent relative to the current column.

The new indention value does not take effect until the following line break.