impressions of tracing recursion from week 4

The tracing recursion is very important in computer science. We do a lot of exercise in the lab, which was very fun. It seems very easy when i first saw it . However, when i wanted to explain why i got those result, i will need to do it step by step. Sometime i will be confuse about when to use the function again. When i need to use recursion to write function, i made some mistake and i can't deal with it that time but i figured it out when i went back t my resident. Anyway, recursion is fun.