Welcome to HCODX Online Compiler
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Ctrl+L Clear output
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Compile and run Racket code online instantly with HCODX. Our free cloud-based Racket compiler supports real-time execution, standard input, syntax highlighting, and code download. No installation or configuration required. Start coding in Racket now.
Run Racket instantly without installing any IDEs or configuring environments. Our cloud-based Racket handles libraries, runtimes, and dependencies automatically so you can focus on writing code.
Whether you are studying algorithms in Racket, practicing data structures in Racket, or exploring functional programming, our tool provides real-time stdout/stderr feedback with interactive standard input support.
HCODX is a free online compiler and code runner: write code in your browser, execute it on a cloud sandbox, and interact with your program through a live terminal. Students use it for coursework and interview practice; developers use it to test snippets in 85+ languages without setting up a local environment.
Racket calls itself a language for making languages — a Scheme descendant re-engineered by the PLT group into a platform where building a new #lang is a library exercise. That research pedigree translated into a teaching empire: 'How to Design Programs' and its student languages introduced program design to a generation of CS students, and Racket still anchors intro and programming-languages courses at Northeastern, Waterloo, Utah, and beyond. The current 8.x series runs on the Chez Scheme backend for a substantially faster runtime. It's also simply a pleasant modern Scheme with batteries: pattern matching, contracts, structs, and big standard libraries. Run Racket on this page in an interactive terminal — read-line takes your typed input live, no DrRacket required.
#lang racket
(display "What's your name? ")
(flush-output)
(define name (read-line))
(printf "Hello, ~a!\n" name)
(display "Enter integers separated by spaces: ")
(flush-output)
(define nums (map string->number (string-split (read-line))))
(printf "Sum: ~a\n" (apply + nums))
(printf "Squares: ~a\n" (map (lambda (n) (* n n)) nums))
(printf "Evens only: ~a\n" (filter even? nums))
(printf "Folded product: ~a\n" (foldl * 1 nums))If your course uses 'How to Design Programs' or covers interpreters and continuations, Racket is your daily driver — and this page lets you run full #lang racket programs from any device when DrRacket isn't installed, such as a library computer or tablet keyboard setup. It's equally good for practicing the functional core that exams test: map/filter/foldl, recursion on lists, higher-order functions, and tail calls. Developers curious about language-oriented programming can prototype S-expression manipulation here before diving into Racket's macro system locally. HCODX is a free online Racket editor, runner and interpreter — an IDE-grade compiler and playground to write and run code online, execute code with live output and live preview, no downloads or web server required.
Yes — both block until you type input, because the program runs against a live terminal rather than a canned stdin. Call (flush-output) after display-ing a prompt without a newline so it appears before the pause. Sequential prompts, then computation, then more prompts all behave as expected.
Yes — a Racket source file begins with a #lang declaration that selects the language, and #lang racket is the standard full language. This is core to Racket's design: the same runtime hosts teaching languages, typed/racket, and user-defined languages. Omitting the line is the most common beginner error.
Programs here run under #lang racket with the main distribution's bundled collections; there is no raco pkg install for third-party packages. HtDP student languages are designed for DrRacket's UI, so translate exercises to plain Racket — usually just swapping (check-expect ...) for direct calls or simple equal? tests.
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