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#include <iostream> #include <functional> using std::placeholders::_1; // to be used in std::bind example int stdf_foobar (int x, std::function<int(int)> moo) { return x + moo(x); // std::function moo called } int foo (int x) { return 2+x; } int foo_2 (int x, in...

While if performs an action only when its condition evaluate to true, if / else allows you to specify the different actions when the condition true and when the condition is false. Example: if (a > 1) puts("a is larger than 1"); else puts("a is not larger than 1"...

globalize gem is a great solution to add translations to your ActiveRecord models. You can install it adding this to your Gemfile: gem 'globalize', '~> 5.0.0' If you're using Rails 5 you will also need to add activemodel-serializers-xml gem 'activemodel-serializers-xml' Model translations...

Due to type erasure the following will not work: public <T> void genericMethod() { T t = new T(); // Can not instantiate the type T. } The type T is erased. Since, at runtime, the JVM does not know what T originally was, it does not know which constructor to call. Workarounds ...

Often you need to change the way a set of data is structured and manipulate certain values. In the example below we got a collection of books with an attached discount amount. But we much rather have a list of books with a price that's already discounted. $books = [ ['title' => 'The Pragma...

In Java, parent and child class both can have static methods with the same name. But in such cases implementation of static method in child is hiding parent class' implementation, it's not method overriding. For example: class StaticMethodTest { // static method and inheritance public stati...

The text-transform property allows you to change the capitalization of text. Valid values are: uppercase, capitalize, lowercase, initial, inherit, and none CSS: .example1 { text-transform: uppercase; } .example2 { text-transform: capitalize; } .example3 { text-transform: lowerc...

This is the easiest syntax to define a function: square(n) = n * n To call a function, use round brackets (without spaces in between): julia> square(10) 100 Functions are objects in Julia, and we can show them in the REPL as with any other objects: julia> square square (generic func...

Arrow syntax Anonymous functions can be created using the -> syntax. This is useful for passing functions to higher-order functions, such as the map function. The below function computes the square of each number in an array A. squareall(A) = map(x -> x ^ 2, A) An example of using this fu...

The following design pattern is categorized as a creational pattern. An abstract factory is used to provide an interface for creating families of related objects, without specifying concrete classes and can be used to hide platform specific classes. interface Tool { void use(); } interf...

pacman is a simple package manager for R. pacman allows a user to compactly load all desired packages, installing any which are missing (and their dependencies), with a single command, p_load. pacman does not require the user to type quotation marks around a package name. Basic usage is as follows:...

Make project (compile modifed and dependent) Windows: Ctrl + F9 OS X / macOS: Cmd + F9 Compile selected file, package or module This is useful to know, as when debugging this shortcut can be used to quickly reload / hotswap classes. Windows: Ctrl + Shift + F9 OS X / macOS: Cmd + Shift + F9 Se...

A basic AppComponent that depends on a single AppModule to provide application-wide singleton objects. @Singleton @Component(modules = AppModule.class) public interface AppComponent { void inject(App app); Context provideContext(); Gson provideGson(); } A module to use to...

A String can be read from an InputStream using the byte array constructor. import java.io.*; public String readString(InputStream input) throws IOException { byte[] bytes = new byte[50]; // supply the length of the string in bytes here input.read(bytes); return new String(bytes); ...

When adding content from sources outside your domain, or from the local file system the canvas is marked as tainted. Attempt to access the pixel data, or convert to a dataURL will throw a security error. vr image = new Image(); image.src = "file://myLocalImage.png"; image.onload = funct...

Say you want to print variables in a 3 character column. Note: doubling { and } escapes them. s = """ pad {{:3}} :{a:3}: truncate {{:.3}} :{e:.3}: combined {{:>3.3}} :{a:>3.3}: {{:3.3}} :{a:3.3}: {{:3.3}} :{c:3...

We can omit the argument in the call if that argument is an Optional Argument Every Optional Argument has its own default value It will take default value if we do not supply the value A default value of a Optional Argument must be a Constant expression. Must be a value type such as enum or s...

Generic interfaces and delegates can have their type parameters marked as covariant or contravariant using the out and in keywords respectively. These declarations are then respected for type conversions, both implicit and explicit, and both compile time and run time. For example, the existing inte...

The IQueryable and IQueryable<T> interfaces allows developers to translate a LINQ query (a 'language-integrated' query) to a specific datasource, for example a relational database. Take this LINQ query written in C#: var query = from book in books where book.Author == "Steph...

To create a function which accepts an undetermined number of arguments, there are two methods depending on your environment. 5 Whenever a function is called, it has an Array-like arguments object in its scope, containing all the arguments passed to the function. Indexing into or iterating over th...