Tutorial by Examples: e

This example will not work because the string passed in isn't recognized as a constant in the project. Even if you pass in "array", it won't work as it isn't capitalized. my_string = "not_a_constant" # => 'not_a_constant' my_string.safe_constantize # => nil my_s...

If you are given a JSON string : val str = """{ | "name" : "Jsony McJsonface", | "age" : 18, | "hobbies" : [ "Fishing", "Hunting", "Camping" ], | "pet" : { | ...

C-style bit manipulation A bit can be set using the bitwise OR operator (|). // Bit x will be set number |= 1LL << x; Using std::bitset set(x) or set(x,true) - sets bit at position x to 1. std::bitset<5> num(std::string("01100")); num.set(0); // num is now 01101 ...

C-style bit-manipulation A bit can be cleared using the bitwise AND operator (&). // Bit x will be cleared number &= ~(1LL << x); Using std::bitset reset(x) or set(x,false) - clears the bit at position x. std::bitset<5> num(std::string("01100")); num.reset(2); ...

C-style bit-manipulation The value of the bit can be obtained by shifting the number to the right x times and then performing bitwise AND (&) on it: (number >> x) & 1LL; // 1 if the 'x'th bit of 'number' is set, 0 otherwise The right-shift operation may be implemented as either a...

C-style bit-manipulation // Bit n will be set if x is 1 and cleared if x is 0. number ^= (-x ^ number) & (1LL << n); Using std::bitset set(n,val) - sets bit n to the value val. std::bitset<5> num(std::string("00100")); num.set(0,true); // num is now 00101 num.set(...

Self-referential association is used to associate a model with itself. The most frequent example would be, to manage association between a friend and his follower. ex. rails g model friendship user_id:references friend_id:integer now you can associate models like; class User < ActiveRecord:...

The ng-required adds or removes the required validation attribute on an element, which in turn will enable and disable the require validation key for the input. It is used to optionally define if an input element is required to have a non-empty value. The directive is helpful when designing validat...

#include <stddef.h> // size_t, ptrdiff_t //----------------------------------- Machinery: using Size = ptrdiff_t; template< class Item, size_t n > constexpr auto n_items( Item (&)[n] ) noexcept -> Size { return n; } //----------------------------------- Us...

// Example of raw dynamic size array. It's generally better to use std::vector. #include <algorithm> // std::sort #include <iostream> using namespace std; auto int_from( istream& in ) -> int { int x; in >> x; return x; } auto main() -> int { ...

// Example of std::vector as an expanding dynamic size array. #include <algorithm> // std::sort #include <iostream> #include <vector> // std::vector using namespace std; int int_from( std::istream& in ) { int x = 0; in >> x; return x; } ...

// A fixed size raw array matrix (that is, a 2D raw array). #include <iostream> #include <iomanip> using namespace std; auto main() -> int { int const n_rows = 3; int const n_cols = 7; int const m[n_rows][n_cols] = // A raw array matrix. ...

Unfortunately as of C++14 there's no dynamic size matrix class in the C++ standard library. Matrix classes that support dynamic size are however available from a number of 3rd party libraries, including the Boost Matrix library (a sub-library within the Boost library). If you don't want a dependenc...

This is useful to see if there are any non-printable characters, or non-ASCII characters. e.g. If you have copy-pasted the code from web, you may have quotes like ” instead of standard ". $ cat -v file.txt $ cat -vE file.txt # Useful in detecting trailing spaces. e.g. $ echo '” ' | c...

Because in .NET 3.5 and older you don't have Lazy<T> class you use the following pattern: public class Singleton { private Singleton() // prevents public instantiation { } public static Singleton Instance { get { return Nested.instanc...

To create a new Rails 5 API, open a terminal and run the following command: rails new app_name --api The following file structure will be created: create create README.rdoc create Rakefile create config.ru create .gitignore create Gemfile create app create app/as...

All collection objects contain a map method that takes a Function as an argument, which must take a single argument. This returns an Iterable backed by the collection. When the Iterable is iterated, each step calls the function with a new element of the collection, and the result of the call becomes...

A typical singleton class : import javax.inject._ @Singleton class BurgersRepository { // implementation goes here } Another class, requiring access to the first one. import javax.inject._ class FastFoodService @Inject() (burgersRepository: BurgersRepository){ // implementation ...

You will often need to access instances of classes from the framework itself (like the WSClient, or the Configuration). You can inject them in your own classes : class ComplexService @Inject()( configuration: Configuration, wsClient: WSClient, applicationLifecycle: ApplicationLifecycle, ...

Basic usage of dependency injection is done by the annotations. When you need to tweak things a little bit, you need custom code to further specify how you want some classes to be instantiated and injected. This code goes in what is called a Module. import com.google.inject.AbstractModule // Pla...