$ include "seed7_05.s7i";

const func array integer: forwardDifference (in array integer: data) is func
  result
    var array integer: diffResult is 0 times 0;
  local
    var integer: index is 0;
  begin
    for index range 1 to pred(length(data)) do
      diffResult &:= -data[index] + data[succ(index)];
    end for;
  end func;

const proc: main is func
  local
    var array integer: data is [] (90, 47, 58, 29, 22, 32, 55, 5, 55, 73);
    var integer: level is 0;
    var integer: number is 0;
    var boolean: firstElement is TRUE;
  begin
    for level range 0 to length(data) do
      firstElement := TRUE;
      for number range data do
        if not firstElement then
          write(", ");
        end if;
        firstElement := FALSE;
        write(number);
      end for;
      writeln;
      data := forwardDifference(data);
    end for;
  end func;