[UPDATE] add accessor fcn. fmt. [TESTS] accessor fcn.

README.md

@@ -1,8 +1,8 @@
-cprod
+Cumulative Product
 ===
 [![NPM version][npm-image]][npm-url] [![Build Status][travis-image]][travis-url] [![Coverage Status][coveralls-image]][coveralls-url] [![Dependencies][dependencies-image]][dependencies-url]
 
-> Computes the cumulative product of a numeric array
+> Computes the cumulative product of an array.
 
 
 ## Installation
@@ -15,39 +15,53 @@ For use in the browser, use [browserify](https://github.com/substack/node-browse
 
 ## Usage
 
-To use the module,
-
 ``` javascript
 var cprod = require( 'compute-cprod' );
 ```
 
-#### cprod( arr )
+#### cprod( arr[, accessor] )
 
-Computes the cumulative product of a numeric `array`.
+Computes the cumulative product of an `array`. For primitive `arrays`,
 
 ``` javascript
 var data = [ 1, 2, 3, 4 ];
 
-cprod( data );
+var arr = cprod( data );
+// returns [ 1, 2, 6, 24 ]
+```
+
+For object `arrays`, provide an accessor `function` for accessing `array` values
+
+``` javascript
+var data = [
+	['beep', 1],
+	['boop', 2],
+	['bap', 3],
+	['baz', 4]
+];
+
+function getValue( d ) {
+	return d[ 1 ];
+}
+
+var arr = cprod( arr, getValue );
 // returns [ 1, 2, 6, 24 ]
 ```
 
+__Note__: the function returns an `array` with a length equal to the original input `array`.
+
+
 
 ## Examples
 
 ``` javascript
 var cprod = require( 'compute-cprod' );
 
 var data = new Array( 10 );
-
 for ( var i = 0; i < data.length; i++ ) {
-  data[ i ] = Math.round( Math.random() * 10 + 1 )  ;
+	data[ i ] = Math.round( Math.random() * 10 ) + 1;
 }
 
-data.sort( function sort( a, b ) {
-  return a - b;
-});
-
 console.log( cprod( data ) );
 // returns [...]
 ```
@@ -59,11 +73,6 @@ $ node ./examples/index.js
 ```
 
 
-## Notes
-
-The function returns an `array` with a length equal to the original input `array`.
-
-
 ## Tests
 
 ### Unit

examples/index.js

@@ -1,15 +1,11 @@
 'use strict';
 
 var cprod = require( './../lib' );
-var data = new Array( 10 );
 
+var data = new Array( 10 );
 for ( var i = 0; i < data.length; i++ ) {
-  data[ i ] = Math.round( Math.random() * 10 + 1 )  ;
+	data[ i ] = Math.round( Math.random()*10 ) + 1;
 }
 
-data.sort( function sort( a, b ) {
-  return a - b;
-});
-
 console.log( cprod( data ) );
 // returns [...]

lib/index.js

@@ -4,7 +4,7 @@
 *
 *
 *	DESCRIPTION:
-*		- Computes the cumulative product of a numeric array
+*		- Computes the cumulative product of an array.
 *
 *
 *	NOTES:
@@ -30,33 +30,78 @@
 
 // MODULES //
 
-// var module_alias = require( 'module_name' );
+var isArray = require( 'validate.io-array' );
 
 
+// CUMULATIVE PRODUCT //
+
 /**
-* FUNCTION: cprod( arr )
-*	Computes the cumulative sum of a numeric array.
+* FUNCTION: cprod( arr[, accessor] )
+*	Computes the cumulative product of an array.
 *
 * @param {Array} arr - numeric array
-* @returns {Array} cumulative sum
+* @param {Function} [accessor] - accessor function for accessing array values
+* @returns {Array} cumulative product
 */
 
-function cprod( arr ) {
-	if ( !Array.isArray( arr ) ) {
-		throw new TypeError( 'cprod()::invalid input argument. Must provide an array.' );
+function cprod( arr, clbk ) {
+	if ( !isArray( arr ) ) {
+		throw new TypeError( 'cprod()::invalid input argument. Must provide an array. Value: `' + arr + '`.' );
+	}
+	if ( arguments.length > 1 ) {
+		if ( typeof clbk !== 'function' ) {
+			throw new TypeError( 'cprod()::invalid input argument. Accessor must be a function. Value: `' + clbk + '`.' );
+		}
 	}
 	var len = arr.length,
-		v = new Array( len );
+		v = new Array( len ),
+		val,
+		flg,
+		i;
 
-	v[ 0 ] = arr[ 0 ];
-	for ( var i = 1; i < len; i++ ) {
-		v[ i ] = v[ i-1 ] * arr[ i ];
+	if ( clbk ) {
+		val = clbk( arr[ 0 ] );
+		if ( val === 0 ) {
+			flg = true;
+		}
+		v[ 0 ] = val;
+		for ( i = 1; i < len; i++ ) {
+			if ( flg ) {
+				v[ i ] = 0;
+				continue;
+			}
+			val = clbk( arr[ i ] );
+			if ( val === 0 ) {
+				flg = true;
+				v[ i ] = 0;
+			} else {
+				v[ i ] = v[ i-1 ] * val;
+			}
+		}
+	} else {
+		val = arr[ 0 ];
+		if ( val === 0 ) {
+			flg = true;
+		}
+		v[ 0 ] = val;
+		for ( i = 1; i < len; i++ ) {
+			if ( flg ) {
+				v[ i ] = 0;
+				continue;
+			}
+			val = arr[ i ];
+			if ( val === 0 ) {
+				flg = true;
+				v[ i ] = 0;
+			} else {
+				v[ i ] = v[ i-1 ] * val;
+			}
+		}
 	}
 	return v;
 } // end FUNCTION cprod()
 
 
-
 // EXPORTS //
 
 module.exports = cprod;

package.json

@@ -1,7 +1,7 @@
 {
   "name": "compute-cprod",
   "version": "0.0.0",
-  "description": "Computes the cumulative product of a numeric array",
+  "description": "Computes the cumulative product of an array.",
   "author": {
     "name": "Philipp Burckhardt",
     "email": "pburckhardt@outlook.com"
@@ -10,6 +10,10 @@
     {
       "name": "Philipp Burckhardt",
       "email": "pburckhardt@outlook.com"
+    },
+    {
+      "name": "Athan Reines",
+      "email": "kgryte@gmail.com"
     }
   ],
   "scripts": {
@@ -31,15 +35,20 @@
     "mathematics",
     "math",
     "cumulative",
-    "product"
+    "product",
+    "prod",
+    "cumprod",
+    "array"
   ],
   "bugs": {
     "url": "https://github.com/compute-io/cprod/issues"
   },
-  "dependencies": {},
+  "dependencies": {
+    "validate.io-array": "^1.0.3"
+  },
   "devDependencies": {
-    "chai": "1.x.x",
-    "mocha": "1.x.x",
+    "chai": "2.x.x",
+    "mocha": "2.x.x",
     "coveralls": "^2.11.1",
     "istanbul": "^0.3.0",
     "jshint": "2.x.x",

test/test.js

@@ -1,3 +1,4 @@
+/* global require, describe, it */
 'use strict';
 
 // MODULES //
@@ -36,7 +37,7 @@ describe( 'compute-cprod', function tests() {
 		];
 
 		for ( var i = 0; i < values.length; i++ ) {
-			expect( badValue( values[i] ) ).to.throw( TypeError );
+			expect( badValue( values[ i ] ) ).to.throw( TypeError );
 		}
 		function badValue( value ) {
 			return function() {
@@ -45,6 +46,28 @@ describe( 'compute-cprod', function tests() {
 		}
 	});
 
+	it( 'should throw an error if provided an accessor which is not a function', function test() {
+		var values = [
+			'5',
+			5,
+			true,
+			undefined,
+			null,
+			NaN,
+			[],
+			{}
+		];
+
+		for ( var i = 0; i < values.length; i++ ) {
+			expect( badValue( values[ i ] ) ).to.throw( TypeError );
+		}
+		function badValue( value ) {
+			return function() {
+				cprod( [], value );
+			};
+		}
+	});
+
 	it( 'should compute the cumulative product', function test() {
 		var data, expected, results;
 
@@ -53,8 +76,71 @@ describe( 'compute-cprod', function tests() {
 
 		results = cprod( data );
 
-		assert.strictEqual( results.length, expected.length );
+		assert.strictEqual( results.length, data.length );
+		assert.deepEqual( results, expected );
+	});
+
+	it( 'should compute the cumulative product using an accessor function', function test() {
+		var data, expected, results;
+
+		data = [
+			{'x':2},
+			{'x':4},
+			{'x':5},
+			{'x':3},
+			{'x':8},
+			{'x':2}
+		];
+		expected = [ 2, 8, 40, 120, 960, 1920 ];
+
+		results = cprod( data, getValue );
+
+		assert.strictEqual( results.length, data.length );
 		assert.deepEqual( results, expected );
+
+		function getValue( d ) {
+			return d.x;
+		}
+	});
+
+	it( 'should zero the array once a zero is encountered', function test() {
+		var data, expected, results;
+
+		data = [ 2, 4, 0, 3, 8, 2 ];
+		expected = [ 2, 8, 0, 0, 0, 0 ];
+
+		results = cprod( data );
+
+		assert.deepEqual( results, expected );
+
+		data = [ 0, 4, 5, 3, 8, 2 ];
+		expected = [ 0, 0, 0, 0, 0, 0 ];
+
+		results = cprod( data );
+
+		assert.deepEqual( results, expected );
+	});
+
+	it( 'should zero the array once a zero is encountered when using an accessor function', function test() {
+		var data, expected, results;
+
+		data = [ 2, 4, 0, 3, 8, 2 ];
+		expected = [ 2, 8, 0, 0, 0, 0 ];
+
+		results = cprod( data, getValue );
+
+		assert.deepEqual( results, expected );
+
+		data = [ 0, 4, 5, 3, 8, 2 ];
+		expected = [ 0, 0, 0, 0, 0, 0 ];
+
+		results = cprod( data, getValue );
+
+		assert.deepEqual( results, expected );
+
+		function getValue( d ) {
+			return d;
+		}
 	});
 
 });