.RKT File Format

Introduction

An .rkt file holds source code in Racket, a language descended from Scheme. It was called PLT Scheme until it was renamed in 2010. Racket is widely used for teaching and for building other languages, and its main implementation runs on Chez Scheme.

Compiled code is cached in compiled/ folders as .zo files. The .rktl extension is used for files loaded directly rather than as modules, and .rktd for plain data.

Structure

A Racket file is UTF-8 text. Each file is one module, and the first line is usually a #lang line naming the language the rest of the file is written in. That may be racket, the smaller racket/base, typed/racket or a language with another syntax entirely, such as scribble/manual for documentation.

In the Racket languages the body is parenthesised forms. Square brackets may be used in place of parentheses, and by habit they mark clauses such as the bindings in a let. require brings in other modules, provide exports names and a main submodule holds code that runs only when the file is run directly. Comments use ;, #| … |# and #;.

#lang racket/base

(provide greet)

; Returns a greeting; the main submodule prints one.
(define (greet name)
  (string-append "Hello, " name))

(module+ main
  (displayln (greet "world")))

Links