samer@0: % loop - Looping feedback arrow for stateful arrows.
samer@0: %
samer@0: % loop ::
samer@0: %    (A, S -> B, S)  ~'function to map input and state to output and next state',
samer@0: %    (size -> S0:S)  ~'function to map size of input to initial state'
samer@0: % -> arrow({A},{B},S) ~'arrow from A to B with state of type S'.
samer@0: 
samer@0: function o=loop(fn,s0)
samer@0: 	if nargin<1, fn=@(a,b)deal(a,b); s0=[]; end
samer@0: 	s.fn=fn; s.s0=s0;
samer@0: 	o=class(s,'loop',arrow(1,1));
samer@0: end
samer@0: