delete method
Implementation
BidiRope delete(int start, int end) {
if (start < 0 || start > length) {
throw RangeError.range(start, 0, length, 'start');
}
if (end < 0 || end > length) {
throw RangeError.range(end, 0, length, 'end');
}
if (start > end) {
throw RangeError('start must be less than or equal to end');
}
if (start == end) {
return this;
}
final newRope = _rope.delete(start, end);
final newText = newRope.toString();
final containsRtl = BidirectionalText.containsRtl(newText);
return BidiRope._(newRope, containsRtl);
}