test-nomh.church

(define my-pi 3.14159265358979323)

(define (glp mean ssq smp)
  (let ([diff (- smp mean)])
    (- (- (/ (* diff diff) (* 2.0 ssq)))
       (* 0.5 (+ (log 2) (log my-pi) (log ssq))))))

(define (randint l h) (+ l (sample-integer (+ 1 (- h l)))))

(define (index-in x xs)
  (define (loop x k rst)
    (if (is_null rst) k
      (if (equal? (first rst) x) k
        (loop x (+ k 1) (rest rst)))))
    (loop x 0 xs))

(define (my-length xs)
  (if (is_null xs) 0
    (+ 1 (my-length (rest xs)))))

(define (data-loop n)
  (if (= n 51) '()
    (pair (list n n)
          (data-loop (+ n 1)))))

(define data (data-loop 0))

(define xbar (/ (sum (map first data)) (my-length data)))

(define (make-sample)
    (define alpha (gaussian 0.0 1e4))
    (define beta (gaussian 0.0 1e4))
    (define tau (abs (gaussian 0.0 1e4)))
    (define (gauss-factor m v x) (factor (glp m v x)))
    (define y-constrs (map (lambda (xy) (gauss-factor (+ alpha (* beta (- (first xy) xbar))) (/ 1.0 tau) (second xy)))
        data))
    (define sample (list alpha beta (/ 1.0 (expt tau 0.5)) tau))
    sample)

(define sample (make-sample))