From 2cd772bdba10ac5b8449595cc218419c33b9bcf4 Mon Sep 17 00:00:00 2001
From: Huon Wilson <dbau.pp+github@gmail.com>
Date: Thu, 10 Oct 2013 13:59:55 +1100
Subject: [PATCH] std::rand: add the Sample and IndependentSample traits.

These are a "parameterised" Rand.
---
 src/libstd/rand/distributions.rs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/libstd/rand/distributions.rs b/src/libstd/rand/distributions.rs
index 0902100dca60..845d8bbc9525 100644
--- a/src/libstd/rand/distributions.rs
+++ b/src/libstd/rand/distributions.rs
@@ -23,6 +23,24 @@
 use num;
 use rand::{Rng,Rand};
 
+/// Things that can be used to create a random instance of `Support`.
+pub trait Sample<Support> {
+    /// Generate a random value of `Support`, using `rng` as the
+    /// source of randomness.
+    fn sample<R: Rng>(&mut self, rng: &mut R) -> Support;
+}
+
+/// `Sample`s that do not require keeping track of state, so each
+/// sample is (statistically) independent of all others, assuming the
+/// `Rng` used has this property.
+// XXX maybe having this separate is overkill (the only reason is to
+// take &self rather than &mut self)? or maybe this should be the
+// trait called `Sample` and the other should be `DependentSample`.
+pub trait IndependentSample<Support>: Sample<Support> {
+    /// Generate a random value.
+    fn ind_sample<R: Rng>(&self, &mut R) -> Support;
+}
+
 mod ziggurat_tables;
 
 // inlining should mean there is no performance penalty for this