Version 1:

```
(define (all-but-last xs)
(cond ((null? xs) (error "all-but-last got empty list!"))
((null? (rest xs)) '())
(else (pair (first xs) (all-but-last (rest xs))))))
(define (all xs)
(if (null? xs)
#t
(and (first xs)
(all (rest xs)))))
(define (noisy-equal? a b)
(flip (if (equal? a b) 1.0 0.2)))
(define samples
(mh-query 10 5
(define bits (repeat 10 (lambda () (if (flip) 1 0))))
bits
(all (map noisy-equal? (rest bits) (all-but-last bits)))))
(for-each display samples)
```

Version 2:

```
(define ising-length 20)
(define non-match-cost (log 0.1))
;; abuses map
(define (bigram xs)
(map list xs (cdr xs)))
(define samples
(mh-query
50 50
(define (eql x y) (factor (if (= x y) 0.0 non-match-cost)))
(define xs (repeat ising-length (lambda () (if (flip) 0 1))))
(for-each (lambda (xy) (eql (car xy) (car (cdr xy)))) (bigram xs))
xs
#t))
(car (reverse samples))
```

Source: shred