Clarity of Mind Foreword Introduction

Installing the REPL and Clarinet

Both the REPL and Clarinet are experimental software. As such, installation procedures may be updated often. It is therefore recommended to consult the documentation of the tool in question in order to install it.

Clarity REPL

A read–eval–print loop (REPL) is an interactive computer programming environment that takes user inputs, evaluates them, and returns the result to the user. The Clarity REPL allows you to play around with the Clarity language and evaluate different expressions. It is very useful for quick tests or to verify the syntax of your code. The REPL is very versatile and can even be packaged up as a web component to be used in the browser (a so called WASM binary). In fact, the interactive snippets found throughout this book are made possible because of it! If you are reading the book online you do not necessarily have to install the REPL, but it is definitely nice to have.

Visit the official GitHub repository for the latest instructions on how to set up the Clarity REPL on your system:


Clarinet is a Clarity runtime packaged as a command line tool, designed to make it easy to write, test, and deploy Clarity smart contracts. Clarinet uses the Clarity REPL under the hood. It is self-contained and provides a built-in testing environment to write tests for your smart contracts. Clarinet is the tool that will be used throughout this book. It will be the basis for all upcoming example projects.

There are two ways to get Clarinet. The first way is to download one of the prebuilt binaries from the GitHub releases page. You will have to download the one particular to your platform, extract it, and then move it to a folder where your command line interface can find it:

  • macOS & Linux: copy the clarinet binary to /usr/local/bin.
  • Windows: copy the clarinet.exe binary to C:\Windows\System32. (A better solution is in the works.)

You can verify Clarinet is installed properly by running clarinet --version in your favourite Terminal emulator.

% clarinet --version
clarinet 0.14.1