Generated by SassMeister.com.

SassMeister-input.scss

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

$v1: 1 2 3;
$v2: 4 5 6;
$v3: 7 8 9;

.test {
  // Is there any shorthand for that? 
  // @Hugo: see the function below
  content: (length($v1) == length($v2)) == (length($v2) == length($v3)); 
  // Why this is not working ? 
  // @Hugo: because this is translated to *is `true` equal `3`?*, which is `false`
  content: ((length($v1) == length($v2)) == length($v3)); 
  // Why this is not working ?
  // @Hugo: same as above
  content: (length($v1) == length($v2) == length($v3));  
}


@function equal-lists($lists...) {
  @if length($lists) < 2 {
    @return true;
  }
  
  $length: length(nth($lists, 1));
  
  @for $i from 2 through length($lists) {
    @if length(nth($lists, $i)) != $length {
      @return false;
    }
  }
  
  @return true;
}

.test {
  content: equal-lists($v1, $v2, $v3);
}

SassMeister-output.css

.test {
  content: true;
  content: false;
  content: false;
}

.test {
  content: true;
}