A Tank is an accumulator. It is fed datum values one at a time until receiving the 'EOS datum value or the Tank itself determines it is done at which point the accumulated value is drained from the Tank and returned.
A Stream is a parameterized type of D datum or the symbols 'Nothing or 'EOS
So for example, a (Stream String). 'EOS denotes an end of stream marker. 'Nothing is a no-op step, and may be viewed as a ’null’ datum value. The envisioned utility of supporting a no-op step is primarily in asynch IO Tanks.
The Continue structure holds the Tank’s continuation or callback procedure. To feed the next datum from the stream into the tank the callback step procedure is invoked with the datum.