Diff of /sml/trunk/src/smlnj-lib/Util/real-order-stats.sml

Parent Directory | Revision Log | Patch

	revision 1732, Thu Dec 16 05:07:47 2004 UTC	revision 1733, Thu Dec 16 05:37:04 2004 UTC
#	Line 8	Line 8
8	*)	*)
9	structure RealOrderStats : sig	structure RealOrderStats : sig
10
11		(* WARNING: Each of the functions exported from this module
12		* modifies its argument array by (partially) sorting it. *)
13
14	(* select the i-th order statistic *)	(* select the i-th order statistic *)
15	val select  : real array * int -> real	val select  : real array * int -> real
16	val select' : real ArraySlice.slice * int -> real	val select' : real ArraySlice.slice * int -> real
#	Line 54	Line 57
57	in rs (p, r) end	in rs (p, r) end
58
59	fun select (a, i) = select0 (a, 0, Array.length a - 1, i)	fun select (a, i) = select0 (a, 0, Array.length a - 1, i)
60	fun select' (s, i) = let val (a, p, l) = ArraySlice.base s	fun select' (s, i) =
61	in select0 (a, p, p+l-1, p+i) end	let val (a, p, l) = ArraySlice.base s in select0 (a, p, p+l-1, p+i) end
62
63	fun median0 (a, p, len) =	fun median0 (a, p, len) =
64	let val mid = p + len div 2	let val mid = p + len div 2
65	val r = p + len - 1	val r = p + len - 1
66	val m0 = select0 (a, p, r, mid)	val m0 = select0 (a, p, r, mid)
67	in if len mod 2 = 1 then m0	fun l(i,m) = if i>=mid then m else l(i+1, Real.max(a$i,m))
68	else let fun l(i,m) = if i>=mid then m else l(i+1, Real.max(a$i,m))	in if len mod 2 = 1 then m0 else (l(p+1,a$p) + m0) / 2.0
	in (l(p+1,a$p) + m0) / 2.0 end
69	end	end
70
71	fun median a = median0 (a, 0, Array.length a)	fun median a = median0 (a, 0, Array.length a)

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