What is Eta REPL?


The Eta REPL allows you to interactively write programs and see the live results. REPL stands for Read-Eval-Print-Loop.

  • Read - reads the expression you type in the prompt
  • Eval - evaluates the given expression
  • Print - prints the result of the evaluation
  • Loop - loops back to the Read step

The Eta REPL is based on Haskell's GHCi with several usability differences.


Interacting with your programs in realtime is a great way to quickly solidfy your understanding of how your application is pieced together and also quickly learn about how new libraries work.

Next Section

In the next section, we'll discuss the philosophy of the Eta REPL.