built-in shelf
#suppress is one of the built-in program output streams.
The #suppress stream is used to discard data. Output can be directed to #suppress
for actions that may produce output that is not wanted. If #suppress is specified with other
destination streams in an output-to, using output as, or put action, then
the data is still written to the other streams. The data is discarded only if #suppress is the only
stream being written to.
#suppress is a markup sink, which means that a markup stream, including both
character data and markup events, may be output to #suppress. Do not use #suppress to
discard a markup stream if any of the markup events is an external entity reference, as the parser may be waiting
for the replacement value.
Markup rules that process content may use the suppress action to discard the
content. The suppress operator sets the current output stream to #suppress, so that any
rules invoked during content processing will also discard their output.
By default, the #suppress stream in any program that uses referents is
treated as if it were opened with referents-displayed.
The #suppress stream always has the h modifier on any text that gets written to
it, which means that line breaking is never carried out on it. Additionally,
the suppress action activates the z modifier, which means that any data content it
encompasses does not go through translate rules.