Outputable is:exact
This module defines classes and functions for pretty-printing. It also
exports a number of helpful debugging and other utilities such as
trace and
panic.
The interface to this module is very similar to the standard Hughes-PJ
pretty printing module, except that it exports a number of additional
functions that are rarely used, and works over the
SDoc type.
Class designating that some type has an
SDoc representation
Values that can be output.