// Convert shorthand to the 4-value syntax

@function unpack($shorthand) {

@if length($shorthand) == 1 {
  @return nth($shorthand, 1) nth($shorthand, 1) nth($shorthand, 1) nth($shorthand, 1);
}
@else if length($shorthand) == 2 {
  @return nth($shorthand, 1) nth($shorthand, 2) nth($shorthand, 1) nth($shorthand, 2);
}
@else if length($shorthand) == 3 {
  @return nth($shorthand, 1) nth($shorthand, 2) nth($shorthand, 3) nth($shorthand, 2);
}
@else {
  @return $shorthand;
}

}