From f07739a5c1cb26ef566a2cccdd8b0d6eb79c4556 Mon Sep 17 00:00:00 2001
From: psnider <snider.peter@gmail.com>
Date: Tue, 24 Mar 2015 14:11:09 +0000
Subject: [PATCH] dice_coefficient supports single character strings

---
 lib/natural/distance/dice_coefficient.js | 34 +++++++++++++++---------
 spec/dice_coefficient_spec.js            |  5 ++++
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/lib/natural/distance/dice_coefficient.js b/lib/natural/distance/dice_coefficient.js
index 52655d373..c8e85c76e 100644
--- a/lib/natural/distance/dice_coefficient.js
+++ b/lib/natural/distance/dice_coefficient.js
@@ -48,22 +48,32 @@ var sanitize = function (str) {
 
 // Compare two strings, and spit out a number from 0-1
 var compare = function (str1, str2) {
-  var pairs1 = wordLetterPairs(sanitize(str1));
-  var pairs2 = wordLetterPairs(sanitize(str2));
+  var sanitized_str1 = sanitize(str1);
+  var sanitized_str2 = sanitize(str2);
+  var pairs1 = wordLetterPairs(sanitized_str1);
+  var pairs2 = wordLetterPairs(sanitized_str2);
   var intersection = 0, union = pairs1.length + pairs2.length;
-  var i, j, pair1, pair2;
-  for (i = 0; i < pairs1.length; i++) {
-    pair1 = pairs1[i];
-    for (j = 0; j < pairs2.length; j++) {
-      pair2 = pairs2[j];
-      if (pair1 == pair2) {
-        intersection ++;
-        delete pairs2[j];
-        break;
+  if (union === 0) {
+      if (sanitized_str1 === sanitized_str2) {
+          return 1;
+      } else {
+          return 0;
+      }
+  } else {
+    var i, j, pair1, pair2;
+    for (i = 0; i < pairs1.length; i++) {
+      pair1 = pairs1[i];
+      for (j = 0; j < pairs2.length; j++) {
+        pair2 = pairs2[j];
+        if (pair1 == pair2) {
+          intersection ++;
+          delete pairs2[j];
+          break;
+        }
       }
     }
+    return 2 * intersection / union;
   }
-  return 2 * intersection / union;
 };
 
 module.exports = compare;
diff --git a/spec/dice_coefficient_spec.js b/spec/dice_coefficient_spec.js
index 9a86ae58b..0e98d4665 100644
--- a/spec/dice_coefficient_spec.js
+++ b/spec/dice_coefficient_spec.js
@@ -6,6 +6,11 @@ describe('dice', function () {
     expect(dice('john', 'john')).toBe(1);
   });
 
+  it('should match single character words', function () {
+    expect(dice('a', 'a')).toBe(1);
+    expect(dice('a', 'b')).toBe(0);
+  });
+
   it('should handle total mis-matches', function () {
     expect(dice('john', 'matt')).toBe(0);
   });