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in operator allows you to check whether a list or a range includes an item: iex(4)> 1 in [1, 2, 3, 4] true iex(5)> 0 in (1..5) false

Unlike a named class or struct, unnamed classes and structs must be instantiated where they are defined, and cannot have constructors or destructors. struct { int foo; double bar; } foobar; foobar.foo = 5; foobar.bar = 4.0; class { int baz; public: int buzz; ...

As a non-standard extension to C++, common compilers allow the use of classes as anonymous members. struct Example { struct { int inner_b; }; int outer_b; //The anonymous struct's members are accessed as if members of the parent struct Example() : inner...

Unnamed class types may also be used when creating type aliases, i.e. via typedef and using: C++11 using vec2d = struct { float x; float y; }; typedef struct { float x; float y; } vec2d; vec2d pt; pt.x = 4.f; pt.y = 3.f;

extern crate serde; extern crate serde_json; #[macro_use] extern crate serde_derive; use std::collections::BTreeMap as Map; #[derive(Serialize)] struct Resource { // Always serialized. name: String, // Never serialized. #[serde(skip_serializing)] hash: String, ...

mutable modifier in this context is used to indicate that a data field of a const object may be modified without affecting the externally-visible state of the object. If you are thinking about caching a result of expensive computation, you should probably use this keyword. If you have a lock (for ...

By default, the implicit operator() of a lambda is const. This disallows performing non-const operations on the lambda. In order to allow modifying members, a lambda may be marked mutable, which makes the implicit operator() non-const: int a = 0; auto bad_counter = [a] { return a++; // er...

Maps and keyword lists have different application. For instance, a map cannot have two keys with the same value and it's not ordered. Conversely, a Keyword list can be a little bit hard to use in pattern matching in some cases. Here's a few use cases for maps vs keyword lists. Use keyword lists wh...

This example shows a simple image cropping function that takes an image and cropping coordinates and returns the cropped image. function cropImage(image, croppingCoords) { var cc = croppingCoords; var workCan = document.createElement("canvas"); // create a canvas workCan.wi...

f = fn {:a, :b} -> IO.puts "Tuple {:a, :b}" [] -> IO.puts "Empty list" end f.({:a, :b}) # Tuple {:a, :b} f.([]) # Empty list

The code listing below attempts to classify handwritten digits from the MNIST dataset. The digits look like this: The code will preprocess these digits, converting each image into a 2D array of 0s and 1s, and then use this data to train a neural network with upto 97% accuracy (50 epochs). "...

struct FileAttributes { unsigned int ReadOnly: 1; unsigned int Hidden: 1; }; Here, each of these two fields will occupy 1 bit in memory. It is specified by : 1 expression after the variable names. Base type of bit field could be any integral type (8-bit int to 64-bit int). Using u...

C++11 In C++11, compilers are required to implicitly move from a local variable that is being returned. Moreover, most compilers can perform copy elision in many cases and elide the move altogether. As a result of this, returning large objects that can be moved cheaply no longer requires special ha...

Let's have a basic failing program: #include <iostream> void fail() { int *p1; int *p2(NULL); int *p3 = p1; if (p3) { std::cout << *p3 << std::endl; } } int main() { fail(); } Build it (add -g to include debug info): g++ -g -o m...

Initializing std::array<T, N>, where T is a scalar type and N is the number of elements of type T If T is a scalar type, std::array can be initialized in the following ways: // 1) Using aggregate-initialization std::array<int, 3> a{ 0, 1, 2 }; // or equivalently std::array<int, 3...

This example has been lifted from the Q & A section here:http://stackoverflow.com/a/1008289/3807729 See this article for a simple design for a lazy evaluated with guaranteed destruction singleton: Can any one provide me a sample of Singleton in c++? The classic lazy evaluated and correctly de...

class API { public: static API& instance(); virtual ~API() {} virtual const char* func1() = 0; virtual void func2() = 0; protected: API() {} API(const API&) = delete; API& operator=(const API&) = delete; }; class WindowsAPI ...

You can generate a rails migration file from the terminal using the following command: rails generate migration NAME [field[:type][:index] field[:type][:index]] [options] For a list of all the options supported by the command, you could run the command without any arguments as in rails generate ...

Type check: variable.isInstanceOf[Type] With pattern matching (not so useful in this form): variable match { case _: Type => true case _ => false } Both isInstanceOf and pattern matching are checking only the object's type, not its generic parameter (no type reification), except fo...

Let's say we need to add a button for each piece of loadedData array (for instance, each button should be a slider showing the data; for the sake of simplicity, we'll just alert a message). One may try something like this: for(var i = 0; i < loadedData.length; i++) jQuery("#container&q...