thunk with a \emph{black hole} (see Black Holes, below). When
evaluation of the thunk completes, the update frame will cause the
thunk to be overwritten again with an \emph{indirection} to the result
thunk with a \emph{black hole} (see Black Holes, below). When
evaluation of the thunk completes, the update frame will cause the
thunk to be overwritten again with an \emph{indirection} to the result