Tutorial by Examples: er

It is possible to detect whether an operator or function can be called on a type. To test if a class has an overload of std::hash, one can do this: #include <functional> // for std::hash #include <type_traits> // for std::false_type and std::true_type #include <utility> // for s...

where clauses can be negated using the where.not syntax: class Person < ApplicationRecord #attribute :first_name, :string end people = Person.where.not(first_name: ['Mark', 'Mary']) # => SELECT "people".* FROM "people" WHERE "people"."first_name&quot...

Elixir comes with integers and floating point numbers. An integer literal can be written in decimal, binary, octal and hexadecimal formats. iex> x = 291 291 iex> x = 0b100100011 291 iex> x = 0o443 291 iex> x = 0x123 291 As Elixir uses bignum arithmetic, the range of int...

If you want to support a url parameter more complex than an id number, you may run into trouble with the parser if the value contains a period. Anything following a period will be assumed to be a format (i.e. json, xml). You can work around this limitation by using a constraint to broaden the accep...

You can use an initializer to set default property values: struct Example { var upvotes: Int init() { upvotes = 42 } } let myExample = Example() // call the initializer print(myExample.upvotes) // prints: 42 Or, specify default property values as a part of the property...

struct MetricDistance { var distanceInMeters: Double init(fromCentimeters centimeters: Double) { distanceInMeters = centimeters / 100 } init(fromKilometers kilos: Double) { distanceInMeters = kilos * 1000 } } let myDistance = MetricDistance(fromCentim...

The Number constructor has some built in constants that can be useful Number.MAX_VALUE; // 1.7976931348623157e+308 Number.MAX_SAFE_INTEGER; // 9007199254740991 Number.MIN_VALUE; // 5e-324 Number.MIN_SAFE_INTEGER; // -9007199254740991 Number.EPSILON; // 0.000...

This is a minimalist module that only slurps files into variables, nothing else. use File::Slurper 'read_text'; my $contents = read_text($filename); read_text() takes two optional parameters to specify the file encoding and whether line endings should be translated between the unixish LF or DOS...

With the use of the extends keyword among classes, all the properties of the superclass (also known as the Parent Class or Base Class) are present in the subclass (also known as the Child Class or Derived Class) public class BaseClass { public void baseMethod(){ System.out.println(&...

A generic class with the type parameter Type class MyGenericClass<Type>{ var value: Type init(value: Type){ self.value = value } func getValue() -> Type{ return self.value } func setValue(value: Type){ self.value = value }...

Euler angles are "degree angles" like 90, 180, 45, 30 degrees. Quaternions differ from Euler angles in that they represent a point on a Unit Sphere (the radius is 1 unit). You can think of this sphere as a 3D version of the Unit circle you learn in trigonometry. Quaternions differ from Eu...

Quaternion.LookRotation(Vector3 forward [, Vector3 up]) will create a Quaternion rotation that looks forward 'down' the forward vector and has the Y axis aligned with the 'up' vector. If the up vector is not specified, Vector3.up will be used. Rotate this Game Object to look at a target Game Object...

Examine the following strings: foobarfoo bar foobar barfoo the regular expression bar will match all four strings, \bbar\b will only match the 2nd, bar\b will be able to match the 2nd and 3rd strings, and \bbar will match the 2nd and 4th strings.

virtual and override The virtual keyword allows a method, property, indexer or event to be overridden by derived classes and present polymorphic behavior. (Members are non-virtual by default in C#) public class BaseClass { public virtual void Foo() { Console.WriteLine("Foo...

First of all, we need to add our first Fragment at the beginning, we should do it in the onCreate() method of our Activity: if (null == savedInstanceState) { getSupportFragmentManager().beginTransaction() .addToBackStack("fragmentA") .replace(R.id.container, FragmentA.n...

Python 2.x2.7 "1deadbeef3".decode('hex') # Out: '\x1d\xea\xdb\xee\xf3' '\x1d\xea\xdb\xee\xf3'.encode('hex') # Out: 1deadbeef3 Python 3.x3.0 "1deadbeef3".decode('hex') # Traceback (most recent call last): # File "<stdin>", line 1, in <module> ...

You can use flatMap(_:) in a similar manner to map(_:) in order to create an array by applying a transform to a sequence's elements. extension SequenceType { public func flatMap<T>(@noescape transform: (Self.Generator.Element) throws -> T?) rethrows -> [T] } The difference with...

Define interface //In this interface, you can define messages, which will be send to owner. public interface MyCustomListener { //In this case we have two messages, //the first that is sent when the process is successful. void onSuccess(List<Bitmap> bitmapList); //And Th...

Returns a random integer between min and max: function randomBetween(min, max) { return Math.floor(Math.random() * (max - min + 1) + min); } Examples: // randomBetween(0, 10); Math.floor(Math.random() * 11); // randomBetween(1, 10); Math.floor(Math.random() * 10) + 1; // randomBet...

public void iterateAndFilter() throws IOException { Path dir = Paths.get("C:/foo/bar"); PathMatcher imageFileMatcher = FileSystems.getDefault().getPathMatcher( "regex:.*(?i:jpg|jpeg|png|gif|bmp|jpe|jfif)"); try (Direc...