samer@3: function Y=diffwith(F,X)
samer@3: % diffwith - Generalised diff using argbitrary binary function
samer@3: %
samer@3: % diffwith :: (A,A->B), seq A -> seq B.
samer@3: %
samer@3: % The given function gets called with the current value as the
samer@3: % first arguments and the previous value as the second. 
samer@3: 
samer@23: 	Y=mapaccum(@diffst,head(X),next(X));
samer@3: 	function [y,s]=diffst(x,s)
samer@3: 		y=F(x,s);
samer@3: 		s=x;
samer@3: 	end
samer@3: end
samer@3: