prompt-hs

A user-friendly, dependently-typed library for asking your users questions

Table of Contents

• Demo
• Usage
• Development Environment
• Building for Production

Demo

module Main (main) where

import Data.Proxy (Proxy (Proxy))
import Data.Text (pack, unpack)
import System.Prompt
  ( Chooseable (showChooseable),
    Confirmation (DontConfirm, RequireConfirmation),
    Requirement (Optional, Required),
    promptChoice,
    promptText,
  )

data Colour = Red | Green | Blue deriving (Bounded, Enum, Eq, Show)

instance Chooseable Colour where
  showChooseable = pack . show

main :: IO ()
main = do
  name <- promptText Required RequireConfirmation $ pack "What is your name?"
  favouriteColour <- promptChoice Optional DontConfirm (Proxy :: Proxy Colour) $ pack "And what is your favourite colour?"
  putStrLn $
    "Your name is " <> unpack name <> " and " <> case favouriteColour of
      Just c -> "your favourite colour is " <> show c
      Nothing -> "you didn't tell me your favourite colour."

Usage

1. Produce an instance of Chooseable for any sum types you want to be able to choose from. For types with Bounded and Enum instances, all you need to provide is how to display the options.
2. Choose a type of prompt: use promptText for freeform text or promptChoice (or promptChoiceFromSet for more flexible options) to get the user to choose one of many options.
3. Requirement: is an answer needed, or can the user skip the question? Can be Required or Optional. 4: Confirmation: If RequireConfirmation, get the user to confirm their answers after selecting/typing. Otherwise, accept it immediately and move on.
4. Give your prompt text.

Note: For Optional questions, the returned value is wrapped in Maybe. For freeform answers, a Just value returned from an Optional question will never be empty.

Development Environment

A development environment is provided:

1. Install Nix
2. Run nix develop

Building for Production

To produce a production build as defined in nix/build.nix, run nix build.

This will produce a result directory with built artefacts.