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Getting Started with PureScript

PureScript is a small strongly, statically typed programming language with expressive types, written in and inspired by Haskell, and compiling to Javascript.

It’s fairly easy to get started with the grunt-init-purescript template

Dependencies

We will need grunt,grunt-init and bower to work with this PureScript template. Node is also a dependency because of this.

bash

npm install -g grunt grunt-init bower

Then clone the template into a .grunt-init folder using git:

bash

mkdir ~/.grunt-init
git clone https://github.com/purescript-contrib/grunt-init-purescript.git ~/.grunt-init/purescript

We also need the PureScript compiler, which we can grab with cabal:

bash

cabal install purescript

Developing

We can now install dependencies from npm and bower. There’s a decent amount to be excited about in the output including purescript-quickcheck, either and maybe to name a few.

bash

npm install
bower update

Then grunt when we want to build:

bash

grunt

Testing

The template project is more of a library project, where the tests are what we want to run if we cloned the repo. As such, our Main module is in tests/Test.purs and can be run using:

bash

node tmp/index.js

after running grunt to build the project.

To build an executable (a node.js scraper for example) we can make a few changes.

Modifications

First, we’ll make some changes to our test file.

Tests

bash

mv tests/Tests.purs tests/Test/Main.purs

and change the module name from Main to Test.Main. Also change the Starter.Kit.Example import to Starter.Kit.Main.

JS

Place two simple js files in js/

js/index.js

bash

require("Starter.Kit.Main").main();

js/test.js

bash

require("Test.Main").main();

Starter Kit

Now we will make a small modification to the Starter Kit file.

bash

mv src/Starter/Kit/Example.purs src/Starter/Kit/Main.purs

and rename the module to Starter.Kit.Main.

Gruntfile

Finally make some modifications to the Gruntfile and run grunt

javascript

module.exports = function(grunt) {
  "use strict";

  grunt.initConfig({
    libFiles: [
      "src/**/*.purs",
      "bower_components/purescript-*/src/**/*.purs"
    ],

    clean: ["tmp", "output"],

    pscMake: {
      lib: {
        src: [""]
      },
      tests: {
        src: ["tests/Test/Main.purs", ""]
      }
    },

    dotPsci: [""],

    copy: [
      {
        expand: true,
        cwd: "output",
        src: ["**"],
        dest: "tmp/node_modules/"
      },
      {
        expand: true,
        cwd: "js/",
        src: "**",
        dest: "tmp/",
        flatten: true
      }
    ],

    execute: {
      tests: {
        src: "tmp/test.js"
      }
    }
  });

  grunt.loadNpmTasks("grunt-contrib-copy");
  grunt.loadNpmTasks("grunt-contrib-clean");
  grunt.loadNpmTasks("grunt-execute");
  grunt.loadNpmTasks("grunt-purescript");

  grunt.registerTask("test", [
    "pscMake:tests",
    "copy",
    "execute:tests"
  ]);
  grunt.registerTask("make", ["pscMake:lib", "dotPsci"]);
  grunt.registerTask("default", ["clean", "make", "test"]);
};