PureScript to Python Compiler

• Specification and Implementation
• Example Project

Get Started

1. *Install a CPython distribution.

   If you’re already a user of CPython, you can skip this step.

   Otherwise, go to this official download page,
   download and install any valid distribution(>=3.5, <=3.8).

1. Install nodejs, which is distributed with a command npm, and use npm to install purescript and its package manager spago. The latest version of the purescript compiler that is supported is 0.13.8:

   npm install -g purescript
   npm install -g spago

   You might check PureScript: Getting Started for more details.

2. Install PureScript-Python components:

   curl -fsSL https://raw.githubusercontent.com/purescript-python/installer/master/install.sh | bash

3. Create an empty folder called hello-world somewhere appropriate,get in, and call

   spago init  # init purescript project
   pspy --init # init purescript-python local configuration

4. Add a key backend with value "pspy", to file spago.dhall of your hello-world project. This is an example:

    {-
    Welcome to a Spago project!
    You can edit this file as you like.
    -}
    { name = "my-project"
    , dependencies = [ "console", "effect", "psci-support" ]
    , packages = ./packages.dhall
    , sources = [ "src/**/*.purs", "test/**/*.purs" ]
    , backend = "pspy" -- !!NOTE THIS!!
    }

5. Write your code in src/**.purs, and use spago run to execute your project(the default entry module is Main).

PureScript Learning Materials

PureScript is close to Haskell, hence a Haskell user can pick it up in few seconds.

The home of PureScript is PureScript.org, where you can find things involving documentations.

HOW-TO: IDE Support

A major motivation for my working on PureScript is its lightweighted but awesome IDE support.

For VSCode users, installing the plugin PureScript IDE and File -> Preferences -> Settings -> (search purescript) -> Turn on "Add Spago sources" will be sufficient. No need to install some GitHub repo and build for 4 hours! And this IDE feels swift!

Troubleshoot pspy-blueprint

If pspy-blueprint provided by the Python package purescripto didn’t work(e.g., users of MacOSX < 10.15), you should manually install it from this repository, and currently there’re 2 options:

1. Install from GitHub release page.
2. Install from source(Need Haskell stack): clone this repo, and use command stack install ., which will install pspy-blueprint to your .local PATH.

For Linux users, you might also need to use chmod u+x <path/to/pspy-blueprint> to allow the permission to execute.

Troubleshoot: Execution Not Sync to Latest Code

This seems to be a recent issue produced by the upstream compiler, and you can resolve this by removing the current output directory:

rm -rf $YOUR_PROJECT_ROOT/output && spago build && pspy --run

This will produce the result of your latest code.