Slashing and rewarding funds

Question

I am trying to understand slashing and rewarding funds from the recipe example.

https://substrate.recipes/currency-imbalances.html

For slashing funds it doesn't require initialization with <NegativeImbalanceOf>::zero() whereas for rewarding funds it requires initializing <PositiveImbalanceOf>::zero()

 //slash fund     
 let imbalance = T::Currency::slash_reserved(&to_punish, collateral).0;
 T::Slash::on_unbalanced(imbalance);

 //reward funds
 let mut total_imbalance = <PositiveImbalanceOf<T>>::zero(); 
 let r = T::Currency::deposit_into_existing(&to_reward, reward).ok();
 total_imbalance.maybe_subsume(r);
 T::Reward::on_unbalanced(total_imbalance);

What does the two extra lines of code do in reward funds, do I have to use it every time I reward funds??

Answer 1

There seems to be no difference here. You can probably simplify the code to:

 //slash fund     
 let imbalance = T::Currency::slash_reserved(&to_punish, collateral).0;
 T::Slash::on_unbalanced(imbalance);

 //reward funds
 let r = T::Currency::deposit_into_existing(&to_reward, reward).ok().unwrap();
 T::Reward::on_unbalanced(r);

Why it was written this way, I cannot speak to, but there is no magic happening or difference between NegativeImbalanceOf and PositiveImbalanceOf.