Variables and Environments

Defining Variables

We use define to assign values to variables.

For example, (define x 2) assigns the value 2 to x:

-> (define x 2)
-> x
2
-> (+ x 5)
7

After calling (define x 2), we say that x is bound to 2. Variable bindings are stored in environments, which we'll talk more about in Unit 3.

Check for Understanding

Suppose the following is typed into the Racket interpreter: 
(define pi 3.14159)
(define radius 3)

(define area (* radius radius pi))
(define circumference (* 2 pi radius))
What would area evaluate to? What would circumference evaluate to?