//<cels>=casc(x,z)
//<cels>=casc(x,z)
//Creates cascade realization of filter
//from a matrix of coefficients
//  x    :(4xN)-Matrix where each column is a cascade
//       :element, the first two column entries being
//       :the numerator coefficients and the second two
//       :column entries being the denominator coefficients
//  z    :Character string representing the cascade variable
//  cels :Resulting cascade representation
//
//EXAMPLE:
//  <> x         =
//
//  !   1.     2.     3.  !
//  !   4.     5.     6.  !
//  !   7.     8.     9.  !
//  !   10.    11.    12. !
//
//  <>cels=casc(x,'z')
//  cels      =
//
//  !             2               2               2  !
//  !   1 + 4z + z      2 + 5z + z      3 + 6z + z   !
//  !  ------------    ------------    ------------  !
//  !              2               2               2 !
//  !   7 + 10z + z     8 + 11z + z     9 + 12z + z  !
//!
//author: F. Delebecque  date: August 1988
   cels=[];
   for col=x,
      nf=[col(1:2);1];
      nd=[col(3:4);1];
      cels=[cels,list('r',poly(nf,'z','c'),poly(nd,'z','c'),[])];
   end,
//end
