I have extremely mixed feelings for this class
hw 10%; 3 quizzes 10% each, lowest dropped; midterms 20% each; final 30%
I would recommend always do the hw, and prepare for the quizzes because that one problem is 10% your grade. The lectures are intense, but as long as you remember all the (tons of) theorems, definitions, lemmas, claims, propositions, and proofs.
For midterm, I believe it is supposed to be finished within an hour. However, leave at least 8h to yourself because the midterms are insanely hard. The final, well, he generously offered 48h, but trust me those 10 problems really needs 2 days to finish.
Tests are insane and he seems to be enjoying that because lots of students gave him that feedback in the reports, but following exams only became more and more tough.

Taking this class was like seeing hell without dying.
In all seriousness, this class is incredibly difficult and time-consuming. At first, I chalked it up to my own ability, but after speaking to classmates and students in other classes, I can't help but feel that this class was unnecessarily difficult. For example, our first midterm was somewhere along 13 parts, for a total of five questions. Meant to take an hour, it took me around 9. Our second midterm, despite our concerns, was even longer and more difficult, being 17 parts and taking me around 12 hours. I believed this to be the norm, but I took a look at the midterms from other classes, which were 3-4 questions, each at most two parts. Furthermore, there are three timed quizzes, which we barely have enough time to complete. The homeworks are incredibly long, 8-10 proofs with multiple parts. They are meant to prepare us for the exams, but it's hard when we don't receive our scores for weeks, and they contain nothing more than vague comments.
I find that the most frustrating thing about this class is the lack of guidance and understanding. While Harris is kind, there isn't much guidance in this class. Despite following his advice, making multiple Piazza posts and attending office hours, I continued to do poorly on the exams. This did significantly impact my mental health negatively, as all of my efforts felt futile. Furthermore, it felt that Harris did not fully understand our capabilities. For many of us, this was our first time writing proofs, and we cannot simply look at problems and know how to solve them. This ultimately led to the exams taking much longer than Harris anticipated.
I'll be honest and say: avoid this class if possible, as Math 115A is a weeder class. If you do have to take this class, my second piece of advice is to avoid Haiyu Huang as your TA. I have never met someone as condescending and rude as him. Any questions you ask will be met with laughter and no effort to hide how imcompetent he finds us to be. Finally, if you are taking this class with this particular professor, make sure you know all the theorems and definitions from lecture and more important homework. I cannout count how many times something proved in homework would've made the exams slightly easier. Additionally, avoid long-winded proofs. As the course went on and I got more discouraged, I began writing the bare minimum on Midterm 2 and the final, and surprisingly, my scores improved marginally.

The tests were insanely hard...24 hour midterms and 48 hour final will take the whole day or two days to complete. There were also three timed quizzes, 2/3 of which were timed very poorly. He does offer extra credit sometimes on the tests/quizzes, although they're usually hard to earn. Lectures have no slides, and the professor writes insanely fast so if you want to actually understand what is being taught then you need to use the recordings / pdfs uploaded after lecture.

Try to take this class with a different professor if you can. If you've never done mathematical proofs before, avoid this prof at all costs (but in general you really should take at least Math 61 before taking 115A). After talking to students with different professors it sounded like this class was a lot harder than the others.

If you’re looking to loathe math and become suicidal, this is the class for you! Unless you already know all the material going into the class, you are pretty much guaranteed to do poorly no matter how much you study. This class is incredibly demoralizing since you could be doing everything you can as a student and still get horrible grades. When you ask Harris questions, he replies with a condescending, harsh tone and often just restates the question and tells you to solve it.
His lectures are horrible and impossible to follow. He doesn't seem to understand that writing at 100mph and skipping steps in proofs is confusing for people that are learning the material for the first time. Every live lecture that I’ve gone to has resulted in me frantically trying to copy the notes while having no time to think about what any of it means. He also never taught us how to write proofs and just expected us to somehow know how to do so.
The weekly homeworks are difficult and ridiculously time consuming. They aren’t graded efficiently, so oftentimes you receive no feedback on your proof writing before being tested on it.
He also gives timed quizzes and 24 hour midterms. The midterms always contain questions that are different from any of the problems we see in lecture or homework. According to Harris, they’re meant to take about an hour, but realistically take around 8 or 9 hours. He asked for feedback after the first midterm as this is his first time teaching a class, and we told him that we thought it was too long. He then proceeded to make the second one even longer and harder. Harris doesn’t have any concept of how long it realistically takes students to finish a test and does not try to change after receiving feedback.
Additionally, the timed quizzes are way too long for the amount of time we are given. Again, we told him that after the first one. He then made the quizzes even longer while only giving us 5 extra minutes, which was nowhere enough time. I did not struggle with a lot of test-taking anxiety prior to taking this class, but during one of the quizzes I was so anxious that I felt like throwing up and ended up dry heaving throughout the entire length of the test. Harris also decided to give us a quiz during week 10, just 5 days before the final.
Our final was outrageously long. Harris said that he wanted to make it “easier” for us by giving us 48 hours to complete the test, so that we could plan around our finals for other classes. However, giving us a 34-part final certainly does NOT make our lives easier. The final took me at least 15 hours, and would have taken longer if I hadn’t given up from being so exhausted. It contained questions unlike any that we had seen before. I do not understand how Harris believed that he was doing us a favor by giving us such a long exam.
Harris also doesn’t curve any of the exam scores. Instead, he just says that he will assign grades accordingly at the end of the quarter and gives vague answers anytime we ask for clarification as to how our grades will be assigned. This causes unnecessary worry and stress for students since we have no idea what our grade in the class might be until it is given to us after the quarter.
No matter how much I studied according to Harris’s advice, I received terrible grades on the exams. I cried before and after nearly all of the quizzes and midterms and during both midterms because the stress was unbearable. I also started dealing with insomnia and suicidal thoughts primarily due to this class. It’s as if Harris wants us to struggle just for the sake of struggling, since it is impossible to actually learn anything in the environment that he creates. He does not take in any of the feedback that we give him, and actively makes students suffer more by doing the opposite of what they ask. Harris does not seem to have even an ounce of empathy or compassion, which makes him a horrendous instructor.
This class has destroyed my life for the past ten weeks. Prior to this quarter, I was a math major and enjoyed the subject. Now, I can confidently say that I do not want to be a math major anymore and in fact, hate math so much that I never want to take a math class ever again. This is easily the worst class I've ever taken in my life. I hope that Harris never gets the opportunity to teach again, since I don’t want any other students to have to deal with him.

The professor was relatively clear and rarely made mistakes during lecture. However, he starts to write very fast around halfway through lecture and begins to rush a bit through the material. In terms of grading, the test were very difficult, as the other review states. It looks like the average was set to a B/B+ as I scored basically around the average on every test and got a B+.

Harris is so nice. Always willing to help, emails back quickly, has plenty of time to meet, cares about his students. He is really good at breaking things down into simpler terms. He would often write out general steps for solving problems which I found really helpful. I did take calculus in high school, but I definitely think even if you had never seen calc before, you would be able to do well with Harris as your prof. I would 100% take a class with Harris again!!

Harris was so helpful! I didn't take any calc in high school, and was still able to be successful in his class because of how easy he was to approach. He is pretty straightforward in lecture and will explain anything you don't understand in office hours (which really helped- super easy to talk to and not intimidating). Although the course required lots of studying, review sessions and office hours REALLY helped so be sure to attend those. I cannot stress enough how great Harris was, especially in OH!

Harris is literally the best professor I have ever had. His explanations are excellent, and if you don't understand something, he goes above and beyond to help you. Before each exam, he send out a practice exam which covers all the topics that will be on the test (make sure you do these, it's literally the exam concepts). His office hours are helpful too, but you need to go in with specific questions and know what you don't know. Even after you leave this class, he offers to help with harder maths classes, grad school and more. 31A is not especially difficult, but Harris makes it so completely manageable. I took this when I was a freshman, and after having other professors at UCLA, I realise what a complete gem Harris was. If you have the change, take him as a prof!!

Harris was a great instructor for this course. Math 31A is very similar to AP Calculus AB, so it helps to have prior knowledge in calculus, but it is definitely not needed with Harris as your instructor. Lectures were very clear, organized, and straightforward; he would explain a theorem and then work out several examples that were similar to the homework. Homework consists of problems from the book, and it was due once a week. There was 1 midterm and 1 final. He also gave us practice problems before the exams, which were VERY similar to the questions on the exams. Lectures were also recorded and posted for review. I highly recommend Harris as an instructor for this class!