$ include "seed7_05.s7i";

const type: combinations is array array integer;

const func combinations: comb (in array integer: arr, in integer: k) is func
  result
    var combinations: combResult is combinations.value;
  local
    var integer: x is 0;
    var integer: i is 0;
    var array integer: suffix is 0 times 0;
  begin
    if k = 0 then
      combResult := 1 times 0 times 0;
    else
      for x key i range arr do
        for suffix range comb(arr[succ(i) ..], pred(k)) do
          combResult &:= [] (x) & suffix;
        end for;
      end for;
    end if;
  end func;

const proc: main is func
  local
    var array integer: aCombination is 0 times 0;
    var integer: element is 0;
  begin
    for aCombination range comb([] (0, 1, 2, 3, 4), 3) do
      for element range aCombination do
        write(element lpad 3);
      end for;
      writeln;
    end for;
  end func;