PROCEDURE BioInvariantChainFromLR3Chain(
    READONLY  p: PZLR3Chain.T; 
    epsilon, delta: LONGREAL; 
  ): REF ARRAY OF INTEGER =
  (*
    Given n equally spaced points along a points sequence 
    computes the corresponding invariant chain.
  *)
  VAR cmax : LONGREAL;
  BEGIN 
    WITH 
      n = NUMBER(p),
      k = NEW(REF ARRAY OF INTEGER, n)
    DO
      cmax := 0.0d0;
      FOR i:= 0 TO n-1 DO 
        WITH 
          x = p[i,0], y = p[i,1], 
          hX = MAX(-3.0d0, Squeeze(x, epsilon, delta)),
          hY = MAX(-3.0d0, Squeeze(y, epsilon, delta)),
          X = ROUND(MIN(+3.0d0, hX)), 
          Y = ROUND(MIN(+3.0d0, hY)) 
        DO 
         k[i] :=  7 * X + Y;    
        END;
      END;
      RETURN k
    END 
END BioInvariantChainFromLR3Chain;