CSSE 304, Day 32

Outline

• Continuation passing interpreter: Basic set-up and If-expressions.

Resources

• Rudimentary interpreter with if-expressions
• Trace of interpreting (if 3 4 5). Notice the interaction between eval-expression and apply-cont.
• Trace of interpreting (if (if 3 4 5) a b). This is where you see why we call it a continuation. When we evaluate

  |(eval-expression
     (lit-exp 4)
        (if-cont (var-exp a) (var-exp b) (halt-cont) (((a b) . #2(3
     4))))
        (((a b) . #2(3 4))))
  

  we are asking "Who needs the value 4?" It is the if-cont we created based on the out if-expression.