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Inheritance among models can be done in two ways: a common abstract class (see the "Model mixins" example) a common model with multiple tables The multi tables inheritance will create one table for the common fields and one per child model example: from django.db import models c...

// An 8-bit 'byte' value: byte aByte = (byte)0b00100001; // A 16-bit 'short' value: short aShort = (short)0b1010000101000101; // Some 32-bit 'int' values: int anInt1 = 0b10100001010001011010000101000101; int anInt2 = 0b101; int anInt3 = 0B101; // The B can be upper or lower case. // A ...

The example reads the first line from a file. It uses an instance of BufferedReader to read data from the file. BufferedReader is a resource that must be closed after the program is finished with it: static String readFirstLineFromFile(String path) throws IOException { try (BufferedReader br = n...

The following example shows other ways you can use the underscore in numeric literals: long creditCardNumber = 1234_5678_9012_3456L; long socialSecurityNumber = 999_99_9999L; float pi = 3.14_15F; long hexBytes = 0xFF_EC_DE_5E; long hexWords = 0xCAFE_BABE; long maxLong = 0x7fff_ffff_ffff_ffffL;...

You can use Map<String, List<String>> myMap = new HashMap<>(); instead of Map<String, List<String>> myMap = new HashMap<String, List<String>>(); However, you can't use List<String> list = new ArrayList<>(); list.add("A"); ...

public String getTypeOfDayWithSwitchStatement(String dayOfWeekArg) { String typeOfDay; switch (dayOfWeekArg) { case "Monday": typeOfDay = "Start of work week"; break; case "Tuesday": case "Wednes...

Detailed instructions on getting caching set up or installed.

// Takes a callback and executes it with the read value def readFile(path: String)(callback: Try[String] => Unit): Unit = ??? readFile(path) { _.flatMap { file1 => readFile(path2) { _.foreach { file2 => processFiles(file1, file2) }} }} The function argument to readFile is...

If shift is called outside of a delimiting reset block, it can be used to create functions that themselves create continuations inside a reset block. It is important to note that shift's type is not just (((A => B) => C) => A), it is actually (((A => B) => C) => (A @cpsParam[B, C])...

We can have three cases to analyze an algorithm: Worst Case Average Case Best Case #include <stdio.h> // Linearly search x in arr[]. If x is present then return the index, // otherwise return -1 int search(int arr[], int n, int x) { int i; for (i=0; i<n; i...

Not everything in a bindings library will have the same name in C# as it does in Java. In C#, interface names start with "I", but Java has no such convention. When you import a Java library, an interface named SomeInterface will become ISomeInterface. Similarly, Java doesn't have propert...

In order to create a workspace, one should run the following in the terminal: $ mkdir -p ~/workspace_name/src $ cd ~/workspace_name/src $ catkin_init_workspace $ cd ~/workspace_name/ $ catkin_make The previous commands creates a workspace named workspace_name. Once a workspace has been creat...

Assuming a workspace named workspace_name has been previously created in the home directory, a package named package_name can be created by executing the following command lines. $ cd ~/workspace_name/src/ $ catkin_create_pkg package_name rospy

The Null literal (written as null) represents the one and only value of the null type. Here are some examples MyClass object = null; MyClass[] objects = new MyClass[]{new MyClass(), null, new MyClass()}; myMethod(null); if (objects != null) { // Do something }...

The if statement is a conditional statement that allows a program to enter or not a specific section of code depending if the condition(s) of the statement are met or not. It can be found in mostly all the existing programming languages. The if statement will usually take the following shape: if(s...

A statement is usually a test on a variable or the return value of a function. To test those values, we can use some relational operators: OperatorMeaningExample==Equal to1 == 1 is TRUE, 1 == 2 is FALSE!=Not equal to1 != 2 is TRUE, 1 != 1 is FALSE<Less than1 < 2 is TRUE, 2 < 1 is FALSE>...

It is possible to ask a program to execute a specific section of code only if an if statement is considered false. For this, we use the else key word. if(statement) { // Code to execute if the statement is true. } else { // Code to execute if the statement is false. } Both code se...

A std::tuple<T...> can be used to pass multiple values around. For example, it could be used to store a sequence of parameters into some form of a queue. When processing such a tuple its elements need to be turned into function call arguments: #include <array> #include <iostream>...

std::integer_sequence itself is about holding a sequence of integers which can be turned into a parameter pack. Its primary value is the possibility to create "factory" class templates creating these sequences: #include <iostream> #include <initializer_list> #include <uti...

Expanding the parameter pack of indices in a comma expression with a value creates a copy of the value for each of the indices. Sadly, gcc and clang think the index has no effect and warn about it (gcc can be silenced by casting the index to void): #include <algorithm> #include <array>...