pull out named fns.
extract commonality.
rename method.
add blah, blah, blah.
add comment.
fish bug.
write type sign of main algo.
changed mind about type signature of algo.
rename fns.
import chunks of.
add points to cluster fn,
tidy up main fns.
rename fn.
rename fn.
rename fn.
make it compile for now.
add type sig.
update type sig.
add convergence check.
change where expr.