Tutorial by Examples: ce

This is an example of how to use the generic type TFood inside Eat method on the class Animal public interface IFood { void EatenBy(Animal animal); } public class Grass: IFood { public void EatenBy(Animal animal) { Console.WriteLine("Grass was eaten by: {0}",...

Code that uses generics has many benefits over non-generic code. Below are the main benefits Stronger type checks at compile time A Java compiler applies strong type checking to generic code and issues errors if the code violates type safety. Fixing compile-time errors is easier than fixing runt...

To filter a slice without allocating a new underlying array: // Our base slice slice := []int{ 1, 2, 3, 4 } // Create a zero-length slice with the same underlying array tmp := slice[:0] for _, v := range slice { if v % 2 == 0 { // Append desired values to slice tmp = append(tmp, ...

Different operations with data are done using special classes. Most of the classes belong to one of the following groups: classification algorithms (derived from sklearn.base.ClassifierMixin) to solve classification problems regression algorithms (derived from sklearn.base.RegressorMixin) to so...

A Service is a component which runs in the background (on the UI thread) without direct interaction with the user. An unbound Service is just started, and is not bound to the lifecycle of any Activity. To start a Service you can do as shown in the example below: // This Intent will be used to star...

The zero value of slice is nil, which has the length and capacity 0. A nil slice has no underlying array. But there are also non-nil slices of length and capacity 0, like []int{} or make([]int, 5)[5:]. Any type that have nil values can be converted to nil slice: s = []int(nil) To test whether a...

PHP 7 introduces a new kind of operator, which can be used to compare expressions. This operator will return -1, 0 or 1 if the first expression is less than, equal to, or greater than the second expression. // Integers print (1 <=> 1); // 0 print (1 <=> 2); // -1 print (2 <=> 1...

A method defined in an interface is by default public abstract. When an abstract class implements an interface, any methods which are defined in the interface do not have to be implemented by the abstract class. This is because a class that is declared abstract can contain abstract method declaratio...

s=this.getChildByName("garbage"); if (s.parent==this) {...} getChildByName() is one of the many functions that can return null if an error occurred when processing its input. Therefore, if you are receiving an object from any function that can possibly return null, check for null first...

interface ITable { // an indexer can be declared in an interface object this[int x, int y] { get; set; } } class DataTable : ITable { private object[,] cells = new object[10, 10]; /// <summary> /// implementation of the indexer declared in the interface //...

This helper validates that the specified attributes are not empty. class Person < ApplicationRecord validates :name, presence: true end Person.create(name: "John").valid? # => true Person.create(name: nil).valid? # => false You can use the absence helper to validate th...

Overload resolution occurs after name lookup. This means that a better-matching function will not be selected by overload resolution if it loses name lookup: void f(int x); struct S { void f(double x); void g() { f(42); } // calls S::f because global f is not visible here, ...

Boolean logic expressions, in addition to evaluating to True or False, return the value that was interpreted as True or False. It is Pythonic way to represent logic that might otherwise require an if-else test. And operator The and operator evaluates all expressions and returns the last expressi...

class File(): def __init__(self, filename, mode): self.filename = filename self.mode = mode def __enter__(self): self.open_file = open(self.filename, self.mode) return self.open_file def __exit__(self, *args): self.open_file.close() ...

Swallowing Exceptions One should always re-throw exception in the following way: try { ... } catch (Exception ex) { ... throw; } Re-throwing an exception like below will obfuscate the original exception and will lose the original stack trace. One should never do this! The st...

Who says you cannot throw multiple exceptions in one method. If you are not used to playing around with AggregateExceptions you may be tempted to create your own data-structure to represent many things going wrong. There are of course were another data-structure that is not an exception would be mor...

Pass an open file object from Python to C extension code. You can convert the file to an integer file descriptor using PyObject_AsFileDescriptor function: PyObject *fobj; int fd = PyObject_AsFileDescriptor(fobj); if (fd < 0){ return NULL; } To convert an integer file descriptor back ...

Simple split of an IP number string. > (lispworks:split-sequence "." "127.0.0.1") ("127" "0" "0" "1") Simple split of an URL: > (lispworks:split-sequence ".:/" "http://127.0.0.1/foo/bar.html" ...

string nullString = null; string emptyString = ""; string whitespaceString = " "; string tabString = "\t"; string newlineString = "\n"; string nonEmptyString = "abc123"; bool result; result = String.IsNullOrEmpty(nullString); ...

Declaring a generic interface interface IResult<T> { wasSuccessfull: boolean; error: T; } var result: IResult<string> = .... var error: string = result.error; Generic interface with multiple type parameters interface IRunnable<T, U> { run(input: T): U; } ...