Working with Modules and Libraries in Racket | Schema Programming Part 8

As your code grows, putting everything in one file becomes unmanageable. Racket's module system helps you organize code into logical, reusable units.

Creating a Module

Every file starting with #lang racket is essentially a module. By default, definitions are private. You must explicitly provide them to make them public.

math-utils.rkt

#lang racket

(provide add-five
         square)

(define (add-five x) (+ x 5))
(define (square x) (* x x))
(define (secret x) "I am hidden") ; Not exported

Using a Module (require)

To use the code from another file, use require.

main.rkt

#lang racket
(require "math-utils.rkt")

(display (add-five 10)) ; 15
; (secret 10) ; Error: unbound identifier

Renaming and prefixing

You can modify imports to avoid naming conflicts.

(require (prefix-in math: "math-utils.rkt"))

(math:square 4)

Installing Third-Party Packages

Racket has a central package repository: pkgs.racket-lang.org.

1. Find a package (e.g., csv-reading).
2. Install it via command line:

   raco pkg install csv-reading
   

3. Require it:

   (require csv-reading)
   

Collections

Standard library modules are often organized into collections.

(require racket/math)
(require racket/list)

Summary

• Provide: Export functions.
• Require: Import functions.
• Raco: The Racket Command-line tool for package management.

In the next part, we'll talk to the outside world: Input/Output and File Handling.