void retainWhere(
bool test(E element)
)

Remove all elements not matched by test.

This method is inefficient since it works by repeatedly removing single elements, each of which can take linear time.

Source

/**
 * Remove all elements not matched by [test].
 *
 * This method is inefficient since it works by repeatedly removing single
 * elements, each of which can take linear time.
 */
void retainWhere(bool test(E element)) {
  _filterWhere(test, false);
}