Logic programming library development log

Computer Science AI in Snap!
111

I have a few questions about procedures on SICP section 4.4.4.2., paragraph "filters":

(define (lisp-value call frame-stream)
_ (stream-flatmap
_ _ (lambda (frame)
_ _ _ (if (execute
_ _ _ _ _ (instantiate
_ _ _ _ _ call
_ _ _ _ _ frame
_ _ _ _ _ (lambda (v f)
_ _ _ _ _ _ (error "Unknown pat var: LISP-VALUE" v))))
_ _ _ _ (singleton-stream frame)
_ _ _ _ the-empty-stream))
_ _ frame-stream))

  • What does call stand for? (is it a predicate?)
  • I was also puzzled by lambda (v f), but I think I know what it stands for now: the lambda function is an unbound variable handler that will ignore its second input - please correct me if I'm wrong.

(define (execute exp)
_ (apply (eval (predicate exp) user-initial-environment)
_ _ _ _ _ (args exp)))

  • Is apply equivalent to reportcall in Snap! ?
  • what is eval equivalent to in Snap! ?
  • what is the user-initial-environment?
  • where does (args exp) come in?

Another question, about sect. 4.4.4.7: what would symbol? translate to in Snap! ?