Use npm package factorial and simplify modulus

component.json

@@ -19,7 +19,8 @@
     "lib/util/contains.js",
     "lib/util/isArray.js",
     "lib/util/isFinite.js",
-    "lib/util/isNaN.js"
+    "lib/util/isNaN.js",
+    "node_modules/factorial/index.js"
   ],
   "license": "MIT"
 }

dist/primality.js

@@ -91,26 +91,14 @@
   };
   require.register("primality/primality.js", function(exports, require, module) {
     var primality;
-    var WILSON_PRIMES = [ 5, 13, 563 ];
-    var _ = require("./lib/util/");
-    function factorial(value) {
-      return value === 0 ? 1 : value * factorial(value - 1);
-    }
-    function mod(x, y) {
-      if (y > 0) {
-        if (x > 0) {
-          return x % y;
-        } else if (x === 0) {
-          return 0;
-        } else {
-          return x - y * Math.floor(x / y);
-        }
-      } else if (y === 0) {
-        return x;
-      } else {
-        throw new Error("Cannot calculate mod for a negative divisor");
-      }
+    var factorial;
+    try {
+      factorial = require("factorial");
+    } catch (e) {
+      factorial = require("./node_modules/factorial/");
     }
+    var _ = require("./lib/util/");
+    var WILSON_PRIMES = [ 5, 13, 563 ];
     function leastFactor(n) {
       if (n === 0) return 0; else if (n % 1 || n * n < 2) return 1; else if (n % 2 === 0) return 2; else if (n % 3 === 0) return 3; else if (n % 5 === 0) return 5;
       var m = Math.sqrt(n);
@@ -147,7 +135,7 @@
       return isRelated(a, b, 6);
     }
     function isWilsonPrime(value) {
-      return _.contains(WILSON_PRIMES, value) ? true : mod(factorial(value - 1) + 1, Math.pow(value, 2)) === 0;
+      return _.contains(WILSON_PRIMES, value) ? true : (factorial(value - 1) + 1) % Math.pow(value, 2) === 0;
     }
     primality.VERSION = "1.5.7";
     primality.areTwinPrimes = areTwinPrimes;
@@ -208,6 +196,11 @@
     }
     module.exports = isNaN;
   });
+  require.register("primality/node_modules/factorial/index.js", function(exports, require, module) {
+    module.exports = function factorial(v) {
+      return v === 0 ? 1 : v * factorial(v - 1);
+    };
+  });
   require.alias("primality/primality.js", "primality/index.js");
   var objectTypes = {
     "boolean": false,

package.json

@@ -29,6 +29,9 @@
     "test": "grunt test",
     "bench": "node perf/index.js"
   },
+  "dependencies": {
+    "factorial": "git://github.com/wearefractal/factorial.git#0ec466f15043e3cf7bb115f3f21b27fda3f3c55b"
+  },
   "devDependencies": {
     "async": "~0.2.0",
     "benchmark": "~1.0.0",

primality.js

@@ -9,49 +9,27 @@
  */
 var primality;
 
-var WILSON_PRIMES = [5, 13, 563];
-
-var _ = require('./lib/util/');
-
 /**
- * Returns the factorial of `value`.
+ * "Hack" to use npm modules as components when they don't have a
+ * `component.json`. This prevents two annoyances:
  *
- * @private
- * @param {Number} value
- * @returns {Number} The factorial of `value`.
- */
-function factorial(value) {
-  return value === 0 ? 1 : value * factorial(value - 1);
-}
-
-/**
- * Returns the modulus of two numbers.
+ *   - bugging the developer to make a `component.json`
+ *   - forking, adding `component.json`, and maintaining this fork
  *
- * @private
- * @param {Number} x
- * @param {Number} y
- * @returns {Number}
+ * First, a regular `require()` is attempted. If that fails, then we must be in
+ * the browser.
  */
-function mod(x, y) {
-  if (y > 0) {
-    if (x > 0) {
-      return x % y;
-    }
-    else if (x === 0) {
-      return 0;
-    }
-    else {
-      return x - y * Math.floor(x / y);
-    }
-  }
-  else if (y === 0) {
-    return x;
-  }
-  else {
-    throw new Error('Cannot calculate mod for a negative divisor');
-  }
+var factorial;
+try {
+  factorial = require('factorial');
+} catch (e) {
+  factorial = require('./node_modules/factorial/');
 }
 
+var _ = require('./lib/util/');
+
+var WILSON_PRIMES = [5, 13, 563];
+
 /**
  * Finds the smallest factor of `n`
  *
@@ -216,7 +194,7 @@ function areSexyPrimes(a, b) {
 function isWilsonPrime(value) {
   return _.contains(WILSON_PRIMES, value)
     ? true
-    : mod(factorial(value - 1) + 1, Math.pow(value, 2)) === 0;
+    : (factorial(value - 1) + 1) % Math.pow(value, 2) === 0;
 }
 
 /**