Add _.unzip. [closes #225]

Former-commit-id: 4b2c7fc068fd430f3d78de850a5f7670fd0e1a4e

build.js

@@ -171,6 +171,7 @@
     'union': ['uniq'],
     'uniq': ['createCallback', 'indexOf'],
     'uniqueId': [],
+    'unzip': ['max', 'pluck'],
     'value': ['forOwn', 'isArray'],
     'values': ['keys'],
     'where': ['filter'],
@@ -258,8 +259,8 @@
     'without'
   ];
 
-  /** List of methods used by Underscore */
-  var underscoreMethods = _.without.apply(_, [allMethods].concat([
+  /** List of Lo-Dash only methods */
+  var lodashOnlyMethods = [
     'at',
     'bindKey',
     'cloneDeep',
@@ -272,8 +273,12 @@
     'merge',
     'parseInt',
     'partialRight',
-    'runInContext'
-  ]));
+    'runInContext',
+    'unzip'
+  ];
+
+  /** List of methods used by Underscore */
+  var underscoreMethods = _.without.apply(_, [allMethods].concat(lodashOnlyMethods));
 
   /** List of ways to export the `lodash` function */
   var exportsAll = [

build/pre-compile.js

@@ -210,6 +210,7 @@
     'uniq',
     'unique',
     'uniqueId',
+    'unzip',
     'value',
     'values',
     'variable',

lodash.js

@@ -222,8 +222,8 @@
      * `invoke`, `keys`, `map`, `max`, `memoize`, `merge`, `min`, `object`, `omit`,
      * `once`, `pairs`, `partial`, `partialRight`, `pick`, `pluck`, `push`, `range`,
      * `reject`, `rest`, `reverse`, `shuffle`, `slice`, `sort`, `sortBy`, `splice`,
-     * `tap`, `throttle`, `times`, `toArray`, `union`, `uniq`, `unshift`, `values`,
-     * `where`, `without`, `wrap`, and `zip`
+     * `tap`, `throttle`, `times`, `toArray`, `union`, `uniq`, `unshift`, `unzip`,
+     * `values`, `where`, `without`, `wrap`, and `zip`
      *
      * The non-chainable wrapper functions are:
      * `clone`, `cloneDeep`, `contains`, `escape`, `every`, `find`, `has`,
@@ -4051,6 +4051,37 @@
       return result;
     }
 
+    /**
+     * The inverse of `_.zip`, this method splits groups of elements into arrays
+     * composed of elements from each group at their corresponding indexes.
+     *
+     * @static
+     * @memberOf _
+     * @category Arrays
+     * @param {Array} array The array to process.
+     * @returns {Array} Returns a new array of the composed arrays.
+     * @example
+     *
+     * _.unzip([['moe', 30, true], ['larry', 40, false]]);
+     * // => [['moe', 'larry'], [30, 40], [true, false]];
+     */
+    function unzip(array) {
+      var index = -1,
+          length = array ? array.length : 0,
+          tupleLength = length ? max(pluck(array, 'length')) : 0,
+          result = Array(tupleLength);
+
+      while (++index < length) {
+        var tupleIndex = -1,
+            tuple = array[index];
+
+        while (++tupleIndex < tupleLength) {
+          (result[tupleIndex] || (result[tupleIndex] = Array(length)))[index] = tuple[tupleIndex];
+        }
+      }
+      return result;
+    }
+
     /**
      * Creates an array with all occurrences of the passed values removed using
      * strict equality for comparisons, i.e. `===`.
@@ -5242,6 +5273,7 @@
     lodash.toArray = toArray;
     lodash.union = union;
     lodash.uniq = uniq;
+    lodash.unzip = unzip;
     lodash.values = values;
     lodash.where = where;
     lodash.without = without;

perf/perf.js

@@ -487,6 +487,10 @@
         var _findWhere = _.findWhere || _.find,\
             lodashFindWhere = lodash.findWhere || lodash.find,\
             whereObject = { "num": 9 };\
+      }\
+      if (typeof zip != "undefined") {\
+        var unzipped = [["a", "b", "c"], [1, 2, 3], [true, false, true]],\
+            zipped = [["a", 1, true], ["b", 2, false], ["c", 3, true]];\
       }'
   });
 
@@ -1752,6 +1756,20 @@
 
   /*--------------------------------------------------------------------------*/
 
+  suites.push(
+    Benchmark.Suite('`_.unzip`')
+      .add(buildName, {
+        'fn': 'lodash.unzip(zipped);',
+        'teardown': 'function zip(){}'
+      })
+      .add(otherName, {
+        'fn': '_.unzip(zipped);',
+        'teardown': 'function zip(){}'
+      })
+  );
+
+  /*--------------------------------------------------------------------------*/
+
   suites.push(
     Benchmark.Suite('`_.values`')
       .add(buildName, '\
@@ -1802,6 +1820,20 @@
 
   /*--------------------------------------------------------------------------*/
 
+  suites.push(
+    Benchmark.Suite('`_.zip`')
+      .add(buildName, {
+        'fn': 'lodash.zip.apply(lodash, unzipped);',
+        'teardown': 'function zip(){}'
+      })
+      .add(otherName, {
+        'fn': '_.zip.apply(_, unzipped);',
+        'teardown': 'function zip(){}'
+      })
+  );
+
+  /*--------------------------------------------------------------------------*/
+
   if (Benchmark.platform + '') {
     log(Benchmark.platform);
   }

test/test-build.js

@@ -118,6 +118,7 @@
     'union',
     'uniq',
     'unique',
+    'unzip',
     'without',
     'zip',
     'zipObject'
@@ -296,8 +297,8 @@
     'without'
   ];
 
-  /** List of methods used by Underscore */
-  var underscoreMethods = _.without.apply(_, [allMethods].concat([
+  /** List of Lo-Dash only methods */
+  var lodashOnlyMethods = [
     'at',
     'bindKey',
     'cloneDeep',
@@ -310,8 +311,12 @@
     'merge',
     'parseInt',
     'partialRight',
-    'runInContext'
-  ]));
+    'runInContext',
+    'unzip'
+  ];
+
+  /** List of methods used by Underscore */
+  var underscoreMethods = _.without.apply(_, [allMethods].concat(lodashOnlyMethods));
 
   /*--------------------------------------------------------------------------*/
 
@@ -970,22 +975,7 @@
         vm.runInContext(data.source, context);
         var lodash = context._;
 
-        _.each([
-          'assign',
-          'at',
-          'bindKey',
-          'createCallback',
-          'findIndex',
-          'findKey',
-          'forIn',
-          'forOwn',
-          'isPlainObject',
-          'merge',
-          'parseInt',
-          'partialRight',
-          'runInContext',
-          'zipObject'
-        ], function(methodName) {
+        _.each(lodashOnlyMethods.concat('assign'), function(methodName) {
           equal(lodash[methodName], undefined, '_.' + methodName + ' should not exist: ' + basename);
         });
 

test/test.js

@@ -2787,6 +2787,58 @@
 
   /*--------------------------------------------------------------------------*/
 
+  QUnit.module('lodash.unzip');
+
+  (function() {
+    var object = {
+      'an empty array': [
+        [],
+        []
+      ],
+      '0-tuples': [
+        [[], []],
+        []
+      ],
+      '1-tuples': [
+        [['moe'], ['larry']],
+        [['moe', 'larry']]
+      ],
+      '2-tuples': [
+        [['moe', 30], ['larry', 40]],
+        [['moe', 'larry'], [30, 40]]
+      ],
+      '3-tuples': [
+        [['moe', 30, true], ['larry', 40, false]],
+        [['moe', 'larry'], [30, 40], [true, false]]
+      ]
+    };
+
+    _.forOwn(object, function(pair, key) {
+      test('should work with ' + key, function() {
+        var actual = _.unzip(pair[0]);
+        deepEqual(actual, pair[1]);
+        deepEqual(_.zip.apply(_, actual), pair[1].length ? pair[0] : pair[1]);
+      });
+    });
+
+    test('should work with tuples of different lengths', function() {
+      var pair = [
+        [['moe', 30], ['larry', 40, false]],
+        [['moe', 'larry'], [30, 40], [undefined, false]]
+      ];
+
+      var actual = _.unzip(pair[0]);
+      ok(1 in actual);
+      deepEqual(actual, pair[1]);
+
+      actual = _.zip.apply(_, actual);
+      ok(2 in actual[0]);
+      deepEqual(actual, [['moe', 30, undefined], ['larry', 40, false]]);
+    });
+  }());
+
+  /*--------------------------------------------------------------------------*/
+
   QUnit.module('lodash.where');
 
   (function() {