Tutorial by Examples: re

Lists Lists can be defined as: data List a = Nil | Cons a (List a) If we translate this into our type algebra, we get List(a) = 1 + a * List(a) But we can now substitute List(a) again in this expression multiple times, in order to get: List(a) = 1 + a + a*a + a*a*a + a*a*a*a + ... ...
You can, of course, return lists from subs: sub foo { my @list1 = ( 1, 2, 3 ); my @list2 = ( 4, 5 ); return ( @list1, @list2 ); } my @list = foo(); print @list; # 12345 But it is not the recommended way to do that unless you know what you are doing. While th...
The auto keyword by itself represents a value type, similar to int or char. It can be modified with the const keyword and the & symbol to represent a const type or a reference type, respectively. These modifiers can be combined. In this example, s is a value type (its type will be inferred as s...
This attaches the results of the query SELECT * FROM Users and sends it to [email protected] EXEC msdb.dbo.sp_send_dbmail @profile_name = 'The Profile Name', @recipients = '[email protected]', @query = 'SELECT * FROM Users', @subject = 'List of users', ...
Returns an integer (int) value that indicates the difference between the soundex values of two character expressions. Parameters: character expression 1. character expression 2. Both parameters are alphanumeric expressions of character data. The integer returned is the number of chars in th...
This is a very basic feature selection technique. Its underlying idea is that if a feature is constant (i.e. it has 0 variance), then it cannot be used for finding any interesting patterns and can be removed from the dataset. Consequently, a heuristic approach to feature elimination is to first re...
auto is used in the syntax for trailing return type: auto main() -> int {} which is equivalent to int main() {} Mostly useful combined with decltype to use parameters instead of std::declval<T>: template <typename T1, typename T2> auto Add(const T1& lhs, const T2& rh...
A simple EntitySystem that processes a Family of entities not once per frame, but after a given interval. Entity processing logic should be placed in processEntity(Entity). For more info, please see IntervalIteratingSystem In the below code example, the best usage for this is the physics world ...
This is a relatively common mistake: You created an rect element, in a bar chart for instance, and you want to add a text label (let's say, the value of that bar). So, using the same variable that you used to append the rect and define its x and y position, you append your text element. Very logic, ...
$ pwd /home/bob/somedir1/somedir2/somedir3 $ pushd /home/bob/otherdir1/otherdir2 /home/bob/otherdir1/otherdir2 /home/bob/somedir1/somedir2/somedir3 $ popd /home/bob/somedir1/somedir2/somedir3 $ pushd /usr /usr /home/bob/somedir1/somedir2/somedir3 $ pushd /var /var /usr /home/bob/som...
6 This can be done using the .repeat() method: "abc".repeat(3); // Returns "abcabcabc" "abc".repeat(0); // Returns "" "abc".repeat(-1); // Throws a RangeError 6 In the general case, this should be done using a correct polyfill for the ES6...
In this question, @Viclib asked about using rewrite rules to exploit typeclass laws to eliminate some overloaded function calls: Mind the following class: class ListIsomorphic l where toList :: l a -> [a] fromList :: [a] -> l a I also demand that toList . fromList == id. H...
Inverts the order of the elements in a sequence. If there is no items throws a ArgumentNullException: source is null. Example: // Create an array. int[] array = { 1, 2, 3, 4 }; //Output: // Call reverse extension method on the array. //4 var reverse = array.R...
To create seeders, you may use the make:seeder Artisan command. All seeders generated will be placed in the database/seeds directory. $ php artisan make:seeder MoviesTableSeeder Generated seeders will contain one method: run. You may insert data into your database in this method. <?php us...
Makes a request only sending part of the form. The text1 value is set, but not text2, as the listener states. Bean.java @ManagedBean @ViewScoped public class Bean { private String text1; private String text2; public String getText1() { return text1; } pu...
Some devices connected through a serial port send data to your program at a constant rate (streaming data) or send data at unpredictable intervals. You can configure the serial port to execute a function automatically to handle data whenever it arrives. This is called the "callback function&quo...
Scala has a powerful type-inference mechanism built-in to the language. This mechanism is termed as 'Local Type Inference': val i = 1 + 2 // the type of i is Int val s = "I am a String" // the type of s is String def squared(x : Int) = x*x // the return type ...
The Scala compiler can also deduce type parameters when polymorphic methods are called, or when generic classes are instantiated: case class InferedPair[A, B](a: A, b: B) val pairFirstInst = InferedPair("Husband", "Wife") //type is InferedPair[String, String] // Equiv...
There are scenarios in which Scala type-inference does not work. For instance, the compiler cannot infer the type of method parameters: def add(a, b) = a + b // Does not compile def add(a: Int, b: Int) = a + b // Compiles def add(a: Int, b: Int): Int = a + b // Equivalent expression, compiles ...
You can group all your custom functions/filters/tests/... inside a custom Twig_Extension class: ProjectTwigExtension class ProjectTwigExtension extends Twig_Extension { public function getFunctions() { return array( new Twig_SimpleFunction('twig_function_name', array($...

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