Outline:

1. Special form: set!
   • evaluating set!
   • set! vs. define
2. Tail-call optimization
   • what it is
   • why it’s useful
   • recognizing tail recursion
3. Wrap-up

What’s next

Upcoming events/assessments:

• CS Bits and Bytes Thursday at 3:30pm in Anderson 329
• Interpreter Parts 4+5 cannot be resubmitted after next Monday at 10pm
• Exam Day 2 will be this Friday (includes Quiz 6 and all other LOs we’ve seen so far)

What you should do now:

• Read the assigned readings (see below)
• Finish Interpreter Part 4: Parser if you haven’t already
• Complete Interpreter Part 5: Evaluating if/let/quote
• Start Interpreter Part 6: Evaluating define/lambda

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

Tail calls (from today):

• Tail calls – stop at “Tail recursion modulo cons”

For next time:

• Read this opinion piece on why Python doesn’t have tail-call optimization (a.k.a. tail recursion elimination)