import Std;

fun printString (s) {
  var i;
  for i := 0, i < s.length, i := i + 1 do
    write (s[i])
  od
}

fun printListConcat ( str_list ) {
	printString (stringcat ( str_list ))
}

var l = { "a" , "b" , "c" , "d" };
printListConcat (l);

l := { "ab" };
printListConcat (l);

l := {};
printListConcat (l)