Computer Science Programming Basics in Ruby

6.2 Array Types

6.2.1 One-Dimensional Arrays

An array is an ordered list of variables. To get the idea, imagine a row of compartments, each of the compartments can contain something or be empty, and they are numbered sequentially starting at 0, as you see on the left side of Figure 6-1.

Arrays start counting their elements, or individual variables, at index 0, as the index is the offset from the beginning of the array. Index 0 is the position of the first element in any array that contains at least one element. Likewise, the n ^th element can be found at index n – 1. Starting at 0 and ending at n – 1 may seem odd, but it is common among most programming languages.

Figure 6-1. Diagram of an array and array access in Ruby

Gem of Wisdom

Array indices are the offset from the first element. As a result, the first element is stored at index 0.

The arrays in Figure 6-1 are known as one-dimensional arrays because there is only one index or dimension. To access an element in an array in Ruby, the notation is array_name[index], where array_name indicates the name of the array and index indicates the element of the array being referenced.

Consider an array named arr that stores a list of five test scores for a student. The student received the scores 73, 98, 86, 61, and 96. The first step of creating an array is the statement: array_name = Array.new. The example code in Example 6-1 ...