/// Return row at `$index` from `$matrix`
/// @group getters
/// @require {function} rows
/// @param {Matrix} $matrix - matrix
/// @param {Number} $index - index
/// @return {List}
@function get-row($matrix, $index) {
  @if type-of($index) != number {
    @warn "Invalid row index.";
    @return false;
  }

  @if abs($index) > rows($matrix) {
    @warn "Out of bound row index.";
    @return false;
  }

  @return nth($matrix, $index);
}