> (set! a 5)
[image] [image] set!: assignment disallowed;
 cannot set variable before its definition
  variable: a
> (define a 5)
> a
5
> (set! a 10)
> a
10
> (define a 5)
> (define a 10)
> a
10
> (define a 20)
> a
20
> (define p (cons 2 3))
> p
(2 . 3)
> (set-car! p 5)
> p
(5 . 3)
> (set-cdr! p 8)
> p
(5 . 8)
> p
(5 . 8)
> (set! (+ 2 3) 8)
[image] set!: not an identifier in: (+ 2 3)
> (set-car! (cons 2 3) 8)
> (begin (+ 2 3) (- 4 5) (* 7 8))
56
> (begin (+ 2 3) (/ 4 0) (* 7 8))
[image] [image] /: division by zero
> (begin (set! a 10) (+ a 20))
30
> a
10
> (define (my-begin . l)
    (last l))
> (my-begin (set! a 30) (+ a 20))
[image] [image] last: undefined;
 cannot reference an identifier before its definition
> (define (last l) (car (reverse l)))
> (my-begin (set! a 30) (+ a 20))
50
> (my-begin (set! a 70) (+ a 20))
90
> begin
[image] begin: bad syntax in: begin
> (my-begin)
[image] [image] mcar: contract violation
  expected: mpair?
  given: ()
> (begin)
> (define (my-begin . l)
    (if (not (null? l)) (last l)))
> (my-begin)
> (begin)
> (let ((x 2)) (+ x (let ((x 3)) (+ x (let ((x 4)) (set! x 5) x)))))
10
> (let ((x 2)) (+ x (let ((x 3)) (+ x (let ((y 4)) (set! x 5) y)))))
9
> (let ((x 2)) (+ x (let ((x 3)) (+ x (let ((y 4)) (+ x y))))))
12
> (let ((x 2)) (+ x (let ((x 3)) (+ x (let ((y 4)) (set! x 5) (+ x y))))))
14
> (let ((x 2)) (+ x (let ((x 3)) (+ x (let ((y 4)) (begin (set! x 5) (+ x y)))))))
14
> p
(5 . 8)
> (set-cdr! p (cons 13 21))
> p
(5 13 . 21)
> (set-cdr! p (cons 13 '()))
> p
(5 13)
> (set-car! (cdr p) 8)
> p
(5 8)
> (set-cdr! (cdr p) p)
> p
#0=(5 8 . #0#)
> (reverse p)
[image] Interactions disabled
> (define p (list 5 8))