pub fn put_back(&mut self, s: I::Item) {
        if self.slot.is_none() {
            self.slot = Some(s);
        } else {
            panic!("PutBack already had a put-back item on-deck!");
        }
    }
/// Put an item back into the iterator. Panics if an item is already on-deck.
Put an item back into the iterator. Panics if an item is already on-deck.
Put an item back into the iterator . Panics if an item is already on - deck .
pub fn put_back(&mut self, s: I::Item) {
        if self.slot.is_none() {
            self.slot = Some(s);
        } else {
            panic!("PutBack already had a put-back item on-deck!");
        }
    }
pub fn put_back ( & mut self , s : I :: Item ) { if self . slot . is_none ( ) { self . slot = Some ( s ) ; } else { panic ! ( " " ) ; } }
Put an item back into the iterator.
Put an item back into the iterator .
&mut self
s
I::Item
&mut self
s
I::Item