Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.14)
// Compass (v1.0.3)
// ----

@function _ss-str-repeat($string, $times, $glue) {
 $result: "";
 $a: ('s', 'ss');
 

 @for $i from 1 through $times {
     @if ($result != "") {
      //$result: $result + $glue;
      //$a: append($result, $string , 'comma');
      $result: append($result, nth($result, length($result))+$glue+$string, 'comma');
     } @else{
       $result: $result+$string;
     }
    //$result: $result + $string;
  }

 @return $result;
}

#{_ss-str-repeat('li', 4, '+')} {
  border: 1px solid #000;
}

SassMeister-output.css

li, li + li, li + li + li, li + li + li + li {
  border: 1px solid #000;
}