Lexical Scope

When an identifier is referred to, it will look for a definition within a local scope. So, in a program like:

(define demo_scope
  (lambda () 
    (let ([y 5])
      (let ([y 9][z (sub1 y)])
        (+ y z)))))

Recursion

(define occurs-in?
  (lambda (x ls)
    (if (null? ls)
        #f
        (if (= x (car ls))
            #t
            (occurs-in? x (cdr ls))))))

Output:

"3.rkt"> occurs-in?
#<procedure:occurs-in?>
"3.rkt"> (occurs-in? 5 '(1 2 3 4))
#f
"3.rkt"> (occurs-in? 5 '(1 2 3 4 5))
#t

Note to self: Revise the section from 19:41 in order to understand the finer details of recursion and something else that I have not initially caught.

So what I get from that is:

Recursion

There is some surrounding context around the recursive call. For example, (+ 1 (a (sub1 p))), where the a is the function, and the recursive callback has the + 1 around it.

Iteration

Not that.