Step by Step solution about How to resolve the algorithm Damm algorithm step by step in the Julia programming language

The Julia code calculates the check digit of a given number according to the Luhn algorithm, which is commonly used for validating identification numbers such as credit card numbers. The check digit is a single digit appended to the end of the number that is used to detect errors in data transmission.

Here's the detailed explanation of the code:

The checkdigit function takes one argument, n, which is the number for which the check digit is to be calculated.

A matrix called matrix is defined within the function. This matrix has 10 rows and 10 columns, and its values are the digits from 0 to 9 in a specific order. The matrix is used to calculate the check digit of the given number.

The variable row is initialized to 0.

A for loop iterates over each character, d, in the string representation of the number n.

Inside the loop, the row is updated using the following formula: row = matrix[row + 1][d - '0' + 1]. Here, d - '0' converts the character representing the digit to the corresponding integer, and + 1 is added because Julia arrays are 1-based. The value at the calculated index in the matrix is assigned to row.

After the loop has iterated over all the digits in the number, the row variable contains the check digit of the number.

The function checkdigit returns the value of row.

The foreach macro is used to apply the checkdigit function to a list of numbers, [5724, 5727, 112946]. The result of the check digit calculation for each number is printed to the console.

The output of the code is as follows:

5724 validates as: true 5727 validates as: false 112946 validates as: true In the output, the first and third numbers validate, meaning that their check digits are correct and the numbers are likely valid. The second number does not validate, indicating a potential error in the number or incorrect input.

function checkdigit(n)
    matrix = (
        (0, 3, 1, 7, 5, 9, 8, 6, 4, 2),
        (7, 0, 9, 2, 1, 5, 4, 8, 6, 3),
        (4, 2, 0, 6, 8, 7, 1, 3, 5, 9),
        (1, 7, 5, 0, 9, 8, 3, 4, 2, 6),
        (6, 1, 2, 3, 0, 4, 5, 9, 7, 8),
        (3, 6, 7, 4, 2, 0, 9, 5, 8, 1),
        (5, 8, 6, 9, 7, 2, 0, 1, 3, 4),
        (8, 9, 4, 5, 3, 6, 2, 0, 1, 7),
        (9, 4, 3, 8, 6, 1, 7, 2, 0, 5),
        (2, 5, 8, 1, 4, 3, 6, 7, 9, 0))
    row = 0
    for d in string(n)
        row = matrix[row + 1][d - '0' + 1]
    end
    return row
end

foreach(i -> println("$i validates as: ", checkdigit(string(i)) == 0), [5724, 5727, 112946])