view signals/TODO @ 61:eff6bddf82e3 tip

Finally implemented perceptual brightness thing.

stateful generators:
	unfold    S -> (X,S)                 loop(0 -> 1)
	scan      (Y,X) -> X                 states(loop(1 -> 0))
	mapaccum  (Y,S) -> (X,S)             loop(1 -> 1)
	zipaccum  (Y1,...,S) -> (X,S)        loop(N -> 1)
	iterate   X -> X                     states(loop(0 -> 0))


signal length?
sndfile from shell pipe