---

title: SICP exercise 3.19

date: 2021-09-02

---

Some content here, before:

```scheme
(define (cycle? l)
  (define (rec l x)
    (cond
      ((null? x) false)
      ((eq? l x) true)
      (true (rec l (cdr x)))))
  (rec l (cdr l)))
```

Sample interactive session:

```scheme
scheme@(guile-user)> (define true #t)
scheme@(guile-user)> (define false #f)
scheme@(guile-user)>
(define (cycle? l)
  (define (rec l x)
    (cond
      ((null? x) false)
      ((eq? l x) true)
      (true (rec l (cdr x)))))
  (rec l (cdr l)))
scheme@(guile-user)> (cycle? '(1 2 3))
$9 = #f
scheme@(guile-user)> (cycle? (make-cycle '(1 2 3)))
$10 = #t
```

# An h1

a list:

1. one
2. two
3. three

some content.

- item
- another
- yet another

## An h2

Xablau:

``` xupliu 1

3 4





dez ```

Foi `wikiwiu`.

a very long code block:

```
wef
wef               wef            wef       wef
wef                                                   wef       wef wef we fwef                wef wef wef            wef 
```

Someone said:

> Xablau, xupliu.

### A repeated header ### A repeated header

a big list:

1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a
1. a