JavaScript
3
Meeting 11 - Operational Semantics
Bor-Yuh Evan Chang
Tuesday, October 1, 2024
Meeting 11 - Operational Semantics
What questions does your neighbor have?
Announcements
- HW1 scores to be released later today
- HW3 due Friday (or Monday?) 6pm
- Peer Reviews on Unit 2 Thu-Fri Oct 3-4 to prepare for the exam
- Exam on Units 1-2 next Tue Oct 8
- 50 minutes in class
- Accommodation letters confirmed (some weeks ago)?
- Look out for note on Piazza about the extended-time location
- During class time
- Practice are all of the learning activities: HWs, Labs, Peer Review
Today
- Feedback Rubric
- Peer Reviews
- Preview HW3
- Operational Semantics
- Triage Your Questions
- Lab 2?
Feedback Rubric
4 - Exceeding (E)
Student has met and exceeded the learning objective.
3 - Proficient (P)
Student has proficiently met the learning objective.
2 - Approaching (A)
Student is approaching the learning objective.
1 - Novice (N)
Student is far from meeting the learning objective.
0 - Zero (Z)
Student has made no attempt towards the learning objective.
Feedback Rubric
4 - Exceeding (E)
Student demonstrates mastery and shows the ability to apply and transfer learning with depth and complexity.
Student demonstrates synthesis of the underlying concepts. Student can go beyond merely describing the solution to explaining the underlying reasoning and discussing generalizations.
3 - Proficient (P)
Student demonstrates competence.
Student is able to explain the overall solution and can answer specific questions. While the student is capable of explaining their solution, they may not be able to confidently extend their explanation beyond the immediate context.
2 - Approaching (A)
Student demonstrates partial understanding.
Student may able to describe the solution but has difficulty answering specific questions about it. Student has difficulty explaining the reasoning behind their solution.
Grading Scale
| Level | Percentage Range | Letter Grade |
|---|---|---|
| Exceeding (E) | 88% – 100% | A |
| 82% – 88% | A- | |
| Proficient (P) | 75% – 82% | B+ |
| 68% – 75% | B | |
| 61% – 68% | B- | |
| 56% – 61% | C+ | |
| 51% – 56% | C | |
| Approaching (A) | 46% – 51% | C- |
| 42% – 46% | D+ | |
| 38% – 42% | D | |
| 34% – 38% | D- |
Peer Reviews
Goal: Staff-organized 30-minute review session to prepare for the exam.
- A day or two before the the sessions, the instructors will release a set of review questions on the unit (think: practice exam questions).
- You sign up for a 30-minute slot to take turns asking each other these questions and giving feedback on where your partner is at on their learning journey (Novice, Approaching, Proficient, Exceeding).
- Show up at your slot with the review questions and your laptop ready. No upfront prep other than completing the homework and lab.
- A member of the Feedback Staff will join most sessions to offer guidance but will not be an interviewer. They are a third-party participant.
- You do not “grade” your partner on their learning level but only assess to what extent your partner was an active participant. The Feedback Staff will do the same.
Questions?
- Review:
- What is relation between judgment forms, inference rules, and judgments?
Questions?
Operational Semantics
Big Picture
What is the purpose of a language specification?
What is the difference between syntax and semantics?
Lab 2: JavaScript is Bananas
How can we describe how to implement a interpreter for all JavaScripty programs?
Evaluation Judgment Form
“Expression
A set of inference rules defining such an evaluation judgment form is called a big-step operational semantics for expressions
Closed Expressions
defined trait Expr defined trait Bop defined class Binary defined class N defined object Plus defined function isValue e_oneplustwo: Binary = Binary(bop = Plus, e1 = N(n = 1.0), e2 = N(n = 2.0))
EvalNum and EvalPlus Rules
EvalNum and EvalPlus Code
defined function eval
Dynamic Typing
Booleans
defined class B defined function isValue e_true: B = B(b = true) e_trueplustwo: Binary = Binary(bop = Plus, e1 = B(b = true), e2 = N(n = 2.0))
EvalVal
defined function eval
MatchError
scala.MatchError: B(true) (of class ammonite.$sess.cmd3$Helper$B) ammonite.$sess.cmd5$Helper.eval(cmd5.sc:6) ammonite.$sess.cmd6$Helper.<init>(cmd6.sc:2) ammonite.$sess.cmd6$.<clinit>(cmd6.sc:7)
DynamicTypeError
defined class DynamicTypeError
defined function eval
TypeError: in expression Binary(Plus,B(true),N(2.0)) ammonite.$sess.cmd9$Helper.eval(cmd9.sc:9) ammonite.$sess.cmd10$Helper.<init>(cmd10.sc:2) ammonite.$sess.cmd10$.<clinit>(cmd10.sc:7)
Coercions
toNumber
defined function toNumber
EvalVal and EvalPlus
Variables
Syntax
defined class Var defined class ConstDecl e_const_i_two_trueplusi: ConstDecl = ConstDecl( x = "i", e1 = N(n = 2.0), e2 = Binary(bop = Plus, e1 = B(b = true), e2 = Var(x = "i")) ) defined type Env empty: Env = Map() defined function lookup defined function extend
Value Environments
Semantics
Variables, Numbers, and Booleans
Meeting 11 - Operational Semantics Bor-Yuh Evan Chang Tuesday, October 1, 2024