Target Sum - return all sets [using Arrays]

program Project1array;
{$APPTYPE CONSOLE}
uses
  System.SysUtils, Generics.Collections;
//
//  Generate a list of all sub-lists that sum to the target figure.
//

type
   TintArr = TArray< integer >;
  TAintArr = TArray< TArray< integer > >;

//  --  --  --  --  --

function ArrPrepend( x : integer; A : TintArr): TintArr;
begin
  insert(x, A, 0);
  ArrPrepend := A;
end;

function ListAppend( A : TintArr; L : TAintArr): TAintArr;
begin
  insert(A, L, high(L)+1);
  ListAppend := L;
end;

//  --  --  --  --  --

function target_sum(const a : TintArr; const k,x : integer) : TAintArr;
begin
  if k > high(a) then begin
                        //result := TAintArr.create();             //  []
                        exit(0);
                      end;

  if x = a[k]    then begin
                        var single :=  TintArr.Create(a[k]);       //  [ a[k] ]
                            result := TAintArr.create(single);     //  [ [a[k]] ]
                        exit;
                      end
  else
                      begin
                        var s := target_sum(a, k + 1, x       );   // not using a[k]
                        var t := target_sum(a, k + 1, x - a[k]);   //     using a[k]

                        for var i  := 0 to high(t) do              // high( [] ) = -1
                            s := ListAppend( ArrPrepend(a[k],t[i]) ,s);
                        result := s;
                      end;
end;

//  --  --  --  --  --

procedure print_list(const list : TintArr);
begin
  for var i in list do write(i, ', ');  writeln;
end;

//  --  --  --  --  --

var
  a :  TintArr;
  s : TAintArr;
const
  target = 0;

begin
  ReportMemoryLeaksOnShutdown := true;

//a := TintArr.Create(1,2,-1,-2);
  a := TintArr.Create(1, 4, 5, 2, 7, 8, -3, -5, -6, 9, 3, -7, -1, 5, 6);
  s := target_sum(a,0,target);

  write('Target = ', target, ' from : '); print_list(a);  writeln;

  if high(s) >0 then for var list in s do print_list(list)
                else writeln('x');
  writeln;
  writeln('# Solutions = ', high(s)+1);
  writeln;

  readln;
end.



(*  Javascript

function target_sum(a, k, x) {
    if (k == a.length) return [];
    if (a[k] == x) {
        return [ [a[k]] ];
    } else {
        var s = target_sum(a, k + 1, x);        // not using a[k]
        var t = target_sum(a, k + 1, x - a[k]); // using a[k]
        for (var i = 0; i < t.length; ++i) {
            t[i].unshift(a[k]);                 // a[k] is part of the solution
            s.push(t[i]);                       // merge t[] into s[]
        }
        return s;
    }
}

var s = target_sum([1, 4, 5, 2, 7, 8, -3, -5, -6, 9, 3, -7, -1, 5, 6], 0, 0);
for (var i = 0; i < s.length; ++i)
    console.log(s[i].join(","));

*)