I am attempting to add discrete uniform distributions to math/distributions.
I have however ran into a type error, I can't fix. Any hints are welcome.
The error:
Type Checker: type mismatch
expected: Discrete-Uniform-Dist
given: (discrete-uniform-dist-struct Real Integer) in: ((inst
discrete-uniform-dist-struct Real Integer) pdf sample cdf inv-cdf min max
median a b)
#lang typed/racket
(require math/distributions racket/flonum math/flonum math/base)
(require math/private/distributions/utils)
; from private/distributions/utils.rkt
(define-real-dist: discrete-uniform-dist Discrete-Uniform-Dist
discrete-uniform-dist-struct ([a : Real] [b : Real]))
(: discrete-uniform : (case-> (-> Discrete-Uniform-Dist)
(-> Integer Discrete-Uniform-Dist)
(-> Integer Integer Discrete-Uniform-Dist)))
(define discrete-uniform
(case-lambda
[() (discrete-uniform 0 1)]
[(b) (discrete-uniform 0 b)]
[(a b) (let ([a (flfloor (fl a))] [b (flfloor (fl b))])
(let ([a (flmin a b)] [b (flmax a b)])
(define pdf (opt-lambda: ([v : Real] [log? : Any #f])
(let ([p (fl/ 1. (fl+ (fl- b a) 1.))])
(if log? (fllog p) p))))
(: sample : (case-> (-> Integer)
(-> Integer (Listof Integer))))
(define sample (let ([a (exact-floor a)] [b (exact-floor
b)])
(case-lambda
[() (random-integer a b)]
[([n : Integer])
(let loop ([i 0])
(if (= i n) '() (cons
(random-integer a b)
(loop (+ i
1)))))])))
(define cdf (opt-lambda: ([v : Real] [log? : Any #f]
[1-p? : Any #f])
(let* ([v (flfloor (fl v))]
[p (cond [(fl< v a) 0.]
[(fl>= v b) 1.]
[else (fl/ (fl+ (fl-
v a) 1.)
(fl+ (fl-
b a) 1.))])])
(cond
[log? (fllog p)]
[1-p? (fl- 1. p)]
[else p]))))
(define inv-cdf (opt-lambda: ([u : Real] [log? : Any #f]
[1-p? : Any #f])
(let* ([u (flfloor (fl u))]
[u (cond
[log? (flexp u)]
[1-p? (fl+ 1. u)]
[else u])])
(exact-floor
(cond [(<= 0. u 1.) (fl+ a (flfloor (*
u (fl+ (fl- b a) 1.))))]
[else 0.])))))
(define min (exact-floor a))
(define max (exact-floor b))
(define median (delay (exact-floor (fl/ (fl+ a b) 2.))))
((inst discrete-uniform-dist-struct Real Integer)
pdf sample cdf inv-cdf min max median a b)))]))
(define X-dist (discrete-uniform 1 11))
(distribution? X-dist)
(sample X-dist)
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
