From 4e4d470626087c26ee18f5cb04c86647b5f2699c Mon Sep 17 00:00:00 2001
From: bculkin2442 <bjculkin@mix.wvu.edu>
Date: Tue, 29 Sep 2015 13:35:50 -0400
Subject: Added random grammar support.

Import of library code from version 1 finished. Now for more library
code and examples on library usage.
---
 .../main/java/bjc/utils/gen/WeightedRandom.java    | 68 ++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 BJC-Utils2/src/main/java/bjc/utils/gen/WeightedRandom.java

(limited to 'BJC-Utils2/src/main/java/bjc/utils/gen/WeightedRandom.java')

diff --git a/BJC-Utils2/src/main/java/bjc/utils/gen/WeightedRandom.java b/BJC-Utils2/src/main/java/bjc/utils/gen/WeightedRandom.java
new file mode 100644
index 0000000..ecd4e36
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/gen/WeightedRandom.java
@@ -0,0 +1,68 @@
+package bjc.utils.gen;
+
+import java.util.Random;
+
+import bjc.utils.funcdata.FunctionalList;
+import bjc.utils.data.GenHolder;
+
+/**
+ * Represents a random number generator where certain results are weighted more heavily than
+ * 		others.
+ * @author ben
+ *
+ * @param <E> The type of values that are randomly selected.
+ */
+public class WeightedRandom<E> {
+	private Random src;
+
+	private FunctionalList<Integer>	probs;
+	private FunctionalList<E>		results;
+
+	private int totalChance;
+
+	/**
+	 * Create a new weighted random generator with the specified source of randomness
+	 * @param sr The source of randomness to use.
+	 */
+	public WeightedRandom(Random sr) {
+		probs = new FunctionalList<>();
+		results = new FunctionalList<>();
+
+		src = sr;
+	}
+
+	/**
+	 * Add a probability for a specific result to be given.
+	 * @param chance The chance to get this result.
+	 * @param res The result to get when the chance comes up.
+	 */
+	public void addProb(int chance, E res) {
+		probs.add(chance);
+		results.add(res);
+
+		totalChance += chance;
+	}
+
+	/**
+	 * Generate a weighted random value.
+	 * @return A random value selected in a weighted fashion.
+	 */
+	public E genVal() {
+		GenHolder<Integer> v = new GenHolder<>(src.nextInt(totalChance));
+		GenHolder<E> res = new GenHolder<E>();
+		GenHolder<Boolean> bl = new GenHolder<>(true);
+
+		probs.forEachIndexed((i, p) -> {
+			if (bl.held) {
+				if (v.held < p) {
+					res.held = results.getByIndex(i);
+					bl.held = false;
+				} else {
+					v.held -= p;
+				}
+			}
+		});
+
+		return res.held;
+	}
+}
-- 
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