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clean up pick-an-index for inclusion in a paper

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Robby Findler 2014-03-25 14:08:44 -05:00
parent b67c3272dc
commit 63f605a93b
1 changed files with 4 additions and 3 deletions
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pkgs/redex-pkgs/redex-lib/redex/private/generate-term.rkt
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@ -287,15 +287,16 @@
(values (enum-ith enum (random-natural the-size))
'ignored))]))
;; pick-an-index : ([0,1] -> Nat) ∪ (-> Nat)
(define (pick-an-index [prob-of-zero 0.01])
(max (random-natural/no-mean prob-of-zero)
(random-natural/no-mean prob-of-zero)
(random-natural/no-mean prob-of-zero)))
;; (: random-natural/no-mean (-> Real Natural))
;; random-natural/no-mean : [0,1] -> Nat
(define (random-natural/no-mean prob-zero)
(define n (exact-floor (sample (geometric-dist prob-zero))))
(define m1 (expt 2 n))
(define x (sample (geometric-dist prob-zero)))
(define m1 (expt 2 (exact-floor x)))
(define m0 (quotient m1 2))
(random-integer m0 m1))