Tutorial by Examples: d

import re precompiled_pattern = re.compile(r"(\d+)") matches = precompiled_pattern.search("The answer is 41!") matches.group(1) # Out: 41 matches = precompiled_pattern.search("Or was it 42?") matches.group(1) # Out: 42 Compiling a pattern allows it to be r...

Given the flavors, the named capture group may looks like this: (?'name'X) (?<name>X) (?P<name>X) With X being the pattern you want to capture. Let's consider the following string: Once upon a time there was a pretty little girl... Once upon a time there was a unicorn with an h...

As you may (or not) know, you can reference a capture group with: $1 1 being the group number. In the same way, you can reference a named capture group with: ${name} \{name} g\{name} Let's take the preceding example and replace the matches with The hero of the story is a ${subject}. T...

A reference cycle (or retain cycle) is so named because it indicates a cycle in the object graph: Each arrow indicates one object retaining another (a strong reference). Unless the cycle is broken, the memory for these objects will never be freed. A retain cycle is created when two instances of ...

BuildConfigField Gradle allows buildConfigField lines to define constants. These constants will be accessible at runtime as static fields of the BuildConfig class. This can be used to create flavors by defining all fields within the defaultConfig block, then overriding them for individual build fla...

# Create the nodes # In a real world scenario we would use at least 3 managers to cover the fail of one manager. docker-machine create -d virtualbox manager docker-machine create -d virtualbox worker1 # Create the swarm # It is possible to define a port for the *advertise-addr* and *listen-ad...

public struct Vector { public int X; public int Y; public int Z; } public struct Point { public decimal x, y; public Point(decimal pointX, decimal pointY) { x = pointX; y = pointY; } } struct instance fields can be set via a p...

Assuming the following Person class: public class Person { public string Name { get; set; } public int Age { get; set; } } The following lambda: p => p.Age > 18 Can be passed as an argument to both methods: public void AsFunc(Func<Person, bool> func) public void AsE...

You can combine object initializers with constructors to initialize types if necessary. Take for example a class defined as such: public class Book { public string Title { get; set; } public string Author { get; set; } public Book(int id) { //do things } // the...

length counts the occurences of elements a in a foldable structure t a. ghci> length [7, 2, 9] -- t ~ [] 3 ghci> length (Right 'a') -- t ~ Either e 1 -- 'Either e a' may contain zero or one 'a' ghci> length (Left "foo") -- t ~ Either String 0 ghci> length (3, True) ...

Any fold can be run in the opposite direction with the help of the Dual monoid, which flips an existing monoid so that aggregation goes backwards. newtype Dual a = Dual { getDual :: a } instance Monoid m => Monoid (Dual m) where mempty = Dual mempty (Dual x) `mappend` (Dual y) = Dua...

To instantiate Foldable you need to provide a definition for at least foldMap or foldr. data Tree a = Leaf | Node (Tree a) a (Tree a) instance Foldable Tree where foldMap f Leaf = mempty foldMap f (Node l x r) = foldMap f l `mappend` f x `mappend` foldMap f r fo...

The function strtok breaks a string into a smaller strings, or tokens, using a set of delimiters. #include <stdio.h> #include <string.h> int main(void) { int toknum = 0; char src[] = "Hello,, world!"; const char delimiters[] = ", !"; char *to...

import Data.Traversable as Traversable data MyType a = -- ... instance Traversable MyType where traverse = -- ... Every Traversable structure can be made a Foldable Functor using the fmapDefault and foldMapDefault functions found in Data.Traversable. instance Functor MyType where ...

When the following is compiled, it will return a different value depending on which directives are defined. // Compile with /d:A or /d:B to see the difference string SomeFunction() { #if A return "A"; #elif B return "B"; #else return "C"; #endif ...

Compiler warnings can be generated using the #warning directive, and errors can likewise be generated using the #error directive. #if SOME_SYMBOL #error This is a compiler Error. #elif SOME_OTHER_SYMBOL #warning This is a compiler Warning. #endif

A compiler symbol is a keyword that is defined at compile-time that can be checked for to conditionally execute specific sections of code. There are three ways to define a compiler symbol. They can be defined via code: #define MYSYMBOL They can be defined in Visual Studio, under Project Propert...

package main import ( "log" "net/http" ) func main() { // Create a mux for routing incoming requests m := http.NewServeMux() // All URLs will be handled by this function m.HandleFunc("/", func(w http.ResponseWriter, r *http.Reque...

C11 Reading an object will cause undefined behavior, if the object is1: uninitialized defined with automatic storage duration it's address is never taken The variable a in the below example satisfies all those conditions: void Function( void ) { int a; int b = a; } 1 (Quo...

// Create an array with a fixed size and type. var array = new Uint8Array(5); // Generate cryptographically random values crypto.getRandomValues(array); // Print the array to the console console.log(array); crypto.getRandomValues(array) can be used with instances of the following classes...