tie | Multiple output version of dplyr : :summarise

For your original desired outcome:

I am missing something trivial

Method equals() should be used for object comparison. Double equals == checks whether two references point to the same object in memory.

If you change the condition inside the comparator to !a.get(0).equals(b.get(0)) it will work correctly.

However, (10001, -10) was put before (10001, -8). Even though -8 is larger than -10.

The reason for such behavior is that JVM caches all the instances of Integer (as well as Byte, Short and Long) in the range [-128; 127]. I.e. these instances are reused, the result of autoboxing of let's say int with a value of 12 will be always the same object.

Because small values in your example like 3, 5, 12 will be represented by a single object, they were compared with == without issues. But the result of comparison with == for two Integer instances with a value of 10001 will be false because in this case there will be two distinct objects in the heap.

The approach of caching frequently used objects is called the Flyweight design pattern. It's very rarely used in Java because this pattern can bring benefits when tons of identical objects are being created and destroyed. Only in such a case caching these objects will pay off with a significant performance improvement. As far as I know, it's used in game development.

Point must be an object, not a list, as Code-Apprentice has pointed out in his answer. Use the power of objects and don't overuse collections. It brings several advantages:

• class provides you a structure, it's easier to organize your code when you are thinking in terms of objects;
• behavior declared inside a class is reusable and easier to test;
• with classes, you can use the power of polymorphism.

Caution: objects could be also misused, one of the possible indicators of that is when a class doesn't declare any behavior apart from getters and its data is being processed somehow in the code outside this class.

Although the notion of point (as a geometrical object) isn't complicated, there are some useful options with regard to methods. For example, you could make instances of the Point class to be able to check to whether they are aligned horizontally or vertically, or whether two points are within a particular radius. And Point class can implement Comparable interface so that points will be able to compare themselves without a Comparator.

With Java 8 method sort() was added to the List interface. It expects an instance of Comparator, and if element of the list implement comparable, and you want them to be sorted according to the natural order null can be passed as an argument.

If the specified comparator is null then all elements in this list must implement the Comparable interface and the elements' natural ordering should be used.

So instead of using utility class Collections you can invoke method sort() directly on a list of points (assuming that Point implements Comparable):

You are correct, this is due to match ergonomics. The first case should hopefully be self explanatory, but the second and third cases can be a bit counter-intuitive.

In the second case:

• (x,) is a non-reference pattern (see the second example in the RFC). The t tuple reference is dereferenced, and x is bound as a ref as it also is a non-reference pattern. Note that t.0 was a reference to begin with, thus resulting in x being a double reference.

• (&y,) is also a non-reference pattern. The t tuple is dereferenced again to a (&i32,). However, &y is a reference pattern being matched to a &i32 reference. Hence y is bound with move mode and is an i32.

In the third case:

• Using the same reasoning as the second case, u is dereferenced via Deref coercion to an (i32,), and x, a non-reference pattern, is bound in ref mode. Hence x is an &i32.

• Again with the same reasoning as the second case, u is dereferenced to an (i32,). The &y reference pattern is then matched to an i32, a non-reference, which causes an error.

This problem has a fun O(n) solution.

If you draw a graph of cumulative sum vs index, then:

The average value in the subarray between any two indexes is the slope of the line between those points on the graph.

The first highest-average-prefix will end at the point that makes the highest angle from 0. The next highest-average-prefix must then have a smaller average, and it will end at the point that makes the highest angle from the first ending. Continuing to the end of the array, we find that...

These segments of highest average are exactly the segments in the upper convex hull of the cumulative sum graph.

Find these segments using the monotone chain algorithm. Since the points are already sorted, it takes O(n) time.

I am just wondering, why do we have to specify the staticfiles based on server in production, when Django could do everything for us as it have always done in localhost?

Because it is likely inefficient and insecure. Each time a request is made, the request passes through all middleware then the view will produce a response that will again pass through the middleware to the client. If you request the same file a second time, it will likely not have any caching, and thus repeat that process again. If you work with a webserver like Nginx/Apache, it will probably cache the result. If you work with a CDN, then it will also contact the nearest server and thus get access to these resources in a more efficient way.

Another problem is security. If you specify a path to a file that is not supposed to be served, then the webserver should prevent the browser from accessing that file. Some hackers for example try to access the source files of the browser to then look for vulnerabilities. This should not be possible. Likely a web server like Apache or Nginx will have more advanced security mechanisms for this in place.

If you really want to, you can use WhiteNoise to let Django serve static files and media files in production. This Django application has been optimized for security and efficiency. Although it is hard to tell if it will have the same level as aan Apache or Nginx server.

Isn't load the files from another storage so much slower than load them from main folder of the project?

The webserver will not contact the other storage: the browser will do that. It thus is possible that instead of the webserver, it will contact a CDN. It is possible that this is slightly less efficient, since a webbrowser usually reuses the open connection to the server to make more requests, but often you already contacted that CDN, for example for JavaScript files. Furthermore CDNs are optimized to deliver content as efficient as possible: the browser will usually contact a browerser close to the client, and usually there is also load balancing and redundancy in place to make it less likely that the server can no longer serve the resource.

It's possible, just annoying to write.

First you need a trait to get parameters from a function type:

libstdc++ does not produce the error while libc++ does.

iostream.objects.overview Concurrent access to a synchronized ([ios.members.static]) standard iostream object's formatted and unformatted input ([istream]) and output ([ostream]) functions or a standard C stream by multiple threads does not result in a data race ([intro.multithread]).

So this looks like a libc++ bug to me.

If you use a query, you would use local component state to set the query parameter

I just reproduced based on the working example what you provided and realized that you set helpers.setTouched manually.

Just don't overuse the setTouched and also you need to handle if you remove the selected item from the autocomplete.