Outline:

1. Recap: lexical vs. dynamic scoping
2. Frames
   • definitions
   • special form: let, revisited
3. Environment model of evaluation
   • overview
   • special form: if
4. [If time] Special forms: let vs. let* vs. letrec
5. Wrap-up

What’s next

Upcoming events/assessments:

• Interpreter Parts 1–3 (linked list + talloc + tokenizer) cannot be resubmitted after Wednesday at 10pm

What you should do now:

• Read the assigned readings (see below)
• Work on resubmitting Interpreter Parts 1–3 with more complete functionality, style fixes, etc.
• Work on Interpreter Part 4: Parser

Reading assignment (to be completed by the next class):

Scheme Environment Model (from today):

• Scheme Environment Model of Evaluation

Lambda and closures (for next time):

• Lambda in Python
• Lambda in Kotlin
• Lambda in Java
• Closures