From 1fe94e41840fb7c8b4f3792fc483b79f69018fa6 Mon Sep 17 00:00:00 2001
From: John Benediktsson <mrjbq7@gmail.com>
Date: Wed, 26 Sep 2012 15:29:08 -0700
Subject: [PATCH] math.extras: adding exponential-index.

---
 extra/math/extras/extras.factor | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/extra/math/extras/extras.factor b/extra/math/extras/extras.factor
index 79fc89d2cb..d011ce80a6 100644
--- a/extra/math/extras/extras.factor
+++ b/extra/math/extras/extras.factor
@@ -185,3 +185,6 @@ PRIVATE>
 : normalized-herfindahl ( seq -- x )
     [ herfindahl ] [ length recip ] bi
     [ - ] [ 1 swap - / ] bi ;
+
+: exponential-index ( seq -- x )
+    dup sum '[ _ / dup ^ ] map-product ;