function X=diffdims(X,Dims)
% diffdims - diff along multiple dimensions
%
% diffdims :: 
%    [D:[[1,E]->natural]]  ~'E dimensional array of size D', 
%    [[K]->[E]]            ~'K dimensions each from 1 to E'
% -> [DD].                 ~'array of diffs, smaller by one in each diffed dim'.

for d=Dims, X=diff(X,1,d); end
