# Seth Barrett

## Daily Blog Post: March 5th, 2023

#### Mar 5th, 2023

An Introduction to Racket: Exploring Data Structures, Functions, and Control Structures

Building on our introduction to Racket, in this post, we will explore some of the language's basic features and introduce new topics such as data structures, functions, and control structures. We will also provide some code examples to illustrate these concepts.

##### Data Structures

Racket provides several built-in data structures, including lists, vectors, and hash tables. Lists are perhaps the most commonly used data structure in Racket, and they can be created using the `list` function:

`(define my-list (list 1 2 3))`

Lists can be manipulated using a variety of functions, such as `cons`, which adds an element to the beginning of a list, and `append`, which concatenates two or more lists. Here's an example that demonstrates these functions:

```(define my-list (list 1 2 3))
(define my-other-list (list 4 5 6))
(define my-new-list (append my-list (cons 0 my-other-list)))```

In this example, we create two lists (`my-list` and `my-other-list`), and then we append `my-list` to a new list that begins with `0` and then contains `my-other-list`.

##### Functions

Functions are a fundamental concept in Racket, and they are defined using the `define` keyword. Here's an example of a simple function that takes two arguments and returns their sum:

```(define (add a b)
(+ a b))```

This function can be called like this:

`(add 1 2) ; returns 3`

Functions can also have optional arguments and default values. Here's an example:

```(define (multiply a b #:c [c 1])
(* a b c))```

This function takes two required arguments (`a` and `b`) and one optional argument (`c`). If `c` is not provided, it defaults to `1`. The `#:c` syntax is used to specify the optional argument.

##### Control Structures

Racket provides several control structures for controlling the flow of execution in a program. The most commonly used control structures are `if`, `cond`, and `case`. Here's an example of an `if` statement:

```(define (is-positive x)
(if (> x 0)
#t
#f))```

This function takes a number `x` as an argument and returns `#t` if `x` is greater than `0`, and `#f` otherwise.

Here's an example of a `cond` statement:

```(define (check-grade grade)
(cond