Optimized `set-nth()` vs old `replace-nth()`

SassMeister-input.scss

// ----
// libsass (v0.7.0)
// ----

/* 
comparison of old and new replace-nth / set-nth
*/

// algorithm copied from early version of sassylists
@function replace-nth($list, $value, $index, $sep: 'comma') {
	$output: ();
	@for $i from 1 through length($list) {
		@if $i == $index { $output: append($output, $value, $sep); }
		@else { $output: append($output, nth($list, $i), $sep); } }
	@return $output;
}

// rewritten algorithm; name and syntax changed to match sass 3.3's 'set-nth()'
// now compensates for sass 3.3 nth() function's changes
@function set-nth($list, $index, $value, $sep: 'comma') {
	$length: length($list); $output: ();
	@if $index > $length or $index <= 0 { @return $list; }
	@if $index > 1 { @for $i from 1 through $index - 1 { $output: append($output, nth($list, $i), $sep); } }
	$output: append($output, $value, $sep);
	@if $length > 1 { @for $i from $index + 1 through $length { $output: append($output, nth($list, $i), $sep); } }
	@return $output;
}

// testing
$mylist: 1 2 3 4 5 6 7;
.test {
  out: replace-nth($mylist, 'yo', 7);
  out: set-nth($mylist, 7, 'yo');
}

SassMeister-output.css

/* 
comparison of old and new replace-nth / set-nth
*/
.test {
  out: 1, 2, 3, 4, 5, 6, 'yo';
  out: 1, 2, 3, 4, 5, 6, 'yo'; }