INDEXES AND RANGE IN C SHARP 8

INDEX

Given a certain Array it is sometimes syntactically inconvenient to access its elements, the indices and ranges in c sharp 8 simplify this management. Let’s clarify the “syntactically awkward” concept with a figure:

Let’s see what indices are.

A new struct System.Index has been introduced in the namespace System.
A new operator has been introduced whose symbol is ^ called (index from end) that is index starting from the end.

RANGE

A new struct System.Range has been introduced in the System namespace.
A new operator has been introduced whose symbol is .. called (range operator) which allows us to take a slice or a slice of value.

using System;
namespace IndiciRange
{
    class Program
    {
        static void Main(string[] args)
        {
           //INDEX
           string[] myArray = {"primo","secondo","terzo","quarto"};
           Index primo = 0;
           Index ultimo = ^1;
           string x = myArray[primo];
           string y = myArray[ultimo];
           Console.WriteLine($"{x} {y}");
           string s1 = myArray[^1];
           string s2 = myArray[^2];
           Console.WriteLine($"{s1} {s2}");
           //RANGE
           string[]a = myArray[..2];   /*- we start from the beginning of the array
                                       and we stop before the specified index 2 */
           foreach(var item in a)
           {
               Console.WriteLine(item);
           }
           string[]b = myArray[2..];  /*--It starts from index two inclusive until the end*/
           foreach(var item in b)
           {
               Console.WriteLine(item);
           }
           string[]c = myArray[1..3];/*--It starts from index 1 included up to index 3 excluded*/
           foreach(var item in c)
           {
               Console.WriteLine(item);
           }
        }
    }
}

INSIGHT

In C#, indexes and ranges are features introduced in C# 8.0 that allow you to work with arrays and strings in a more convenient way. Here is a detailed explanation of how they work:

Indexes

Indexes represent a position in a collection (such as an array or string). In C#, indexes can be either positive or negative:

– Positive indexes start from 0 (for the first element) to length – 1 (for the last element).

– Negative indexes start from -1 (for the last element) to -length (for the first element).

C# introduces the Index structure to represent indexes. This structure provides a convenient way to access elements from the beginning or end of the collection.

Example:

int[] array = { 1, 2, 3, 4, 5 };
Console.WriteLine(array[^1]); // Output: 5 (ultimo elemento)

Range

A range represents a subsection of a collection. In C#, ranges are represented by the Range structure, which uses two indexes to specify the beginning and end of the range.

Example:

int[] array = { 1, 2, 3, 4, 5 };
int[] subArray = array[1..3]; // Contiene gli elementi da array[1] a array[2], escluso array[3]
foreach (var item in subArray)
{
Console.WriteLine(item); // Output: 2 3
}

Syntax of Indexes and Ranges

– To create an index from the beginning of the collection: Index index = 0;

– To create an index from the end of the collection: Index index = ^1;

– To create a range that includes elements from index 1 to index 3 (excluding): Range range = 1..3;

– To create a range that includes all elements from index 1 to the end: Range range = 1..;

– To create a range that includes all elements from the beginning to index 3 (excluding): Range range = ..3;

– To create a range that includes all elements: Range range = ..;

Practical Examples

Using Indexes

string text = “Hello, World!“;
char lastChar = text[^1]; // Ottiene l’ultimo carattere ‘!’
char secondLastChar = text[^2]; // Ottiene il penultimo carattere ‘d’
Console.WriteLine(lastChar); // Output: !
Console.WriteLine(secondLastChar); // Output: d

Using Range

string text = “Hello, World!“;
string subText = text[7..12]; // Ottiene la sottostringa “World”
Console.WriteLine(subText); // Output: World

int[] numbers = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
int[] subArray = numbers[3..7]; // Ottiene gli elementi {3, 4, 5, 6}
foreach (var number in subArray)
{
Console.WriteLine(number); // Output: 3 4 5 6
}