fix bisection.left

README.md

@@ -5,6 +5,11 @@
 1. [Node.js](http://nodejs.org/)
 2. `npm install bisection`
 
+# PROPERTIES
+
+1. half-inclusive, index of x = [ bisection.left(list, x) , bisection.right(list, x) )
+2. number of x in list = bisection.right(list, x) - bisection.left(list, x)
+
 # UNIT TESTS
 
 ```

index.js

@@ -37,6 +37,7 @@ bisection.right = bisection;
 
 /**
  * Calculates the index of the Array where item X should be placed, assuming the Array is sorted.
+ *
  * @param {Array} array The array containing the items.
  * @param {number} x The item that needs to be added to the array.
  * @param {number} low Inital Index that is used to start searching, optional.
@@ -54,10 +55,10 @@ bisection.left = function left( array, x, low , high ){
   while (low < high) {
     mid = (low + high) >> 1;
 
-    if (x < array[mid]) {
-      low = mid + 1;
-    } else {
+    if (x <= array[mid]) {
       high = mid;
+    } else {
+      low = mid + 1;
     }
   }
 
@@ -67,6 +68,6 @@ bisection.left = function left( array, x, low , high ){
 /**
  * Library version
  */
-bisection.version = '0.0.3';
+bisection.version = '0.0.4';
 
 module.exports = bisection;

package.json

@@ -4,7 +4,7 @@
   "author": "Arnout Kazemier",
   "description": "A JavaScript port of the bisection algorithm that is used in Python",
   "scripts": {
-    "test": "node tests/bisection.test.js"
+    "test": "make test"
   },
   "keywords": [
     "algorithm",

tests/bisection.test.js

@@ -21,16 +21,22 @@ module.exports = {
     bisection(large, 242).should.equal(4);
     bisection(large, 0).should.equal(0);
     bisection(large, 232424).should.equal(14);
+
   }
 , 'Bisection left': function(){
-    bisection.left(small, 4).should.equal(9);
-    bisection.left(small, 15).should.equal(0);
-    bisection.left(small, 4, 5).should.equal(9);
-    bisection.left(small, 12, 0, 5).should.equal(0);
-
-    bisection.left(large, 350).should.equal(0);
-    bisection.left(large, 242).should.equal(14);
-    bisection.left(large, 0).should.equal(14);
-    bisection.left(large, 232424).should.equal(0);
+    bisection.left(small, 4).should.equal(4);
+    bisection.left(small, 15).should.equal(9);
+    bisection.left(small, 4, 5).should.equal(5);
+    bisection.left(small, 12, 0, 5).should.equal(5);
+    bisection.left(large, 350).should.equal(8);
+    bisection.left(large, 242).should.equal(4);
+    bisection.left(large, 0).should.equal(0);
+    bisection.left(large, 232424).should.equal(14);
+  }
+, 'Bisection count': function(){
+    (bisection.right(small, 3) - bisection.left(small, 3)).should.equal(1);
+    (bisection.right(small, 4) - bisection.left(small, 4)).should.equal(0);
+    (bisection.right(large, 122) - bisection.left(large, 122)).should.equal(1);
+    (bisection.right(large, 4) - bisection.left(large, 4)).should.equal(0);
   }
 };