Say I have `NSArray *x = @[@1, @2, @3, @4];`

Now say I want an array like `@[@2, @4, @6, @8]`

In good ole Swift, I can just do :

```
xDoubled = x.map({($0) * 2})

```

Can someone tell me how I can do this in Objective-C without doing -

```
NSMutableArray *xDoubled = [NSMutableArray new];
for (NSInteger xVal in x) {
    [xDoubled addObject:xVal * 2];
}

```

?