The purpose of this repository is to present an introduction to functional programming by way of PureScript. PureScript is a language focused on providing features normally associated with Haskell offshoots, but in the context of JavaScript.

As such, it's built on a foundation of pure functional programming that is very suitable for teaching and expressing abstraction via functions and data structures.

There is an overview of some differences and similarities between PureScript and TypeScript here.

Run the following in order to set the project up:

yarn
yarn spago build

If you are running VSCode, add the following options in your preferences, either for the workspace or your general install (as they are generally useful):

"purescript.addSpagoSources": true,
"purescript.addNpmPath": true,
"purescript.buildCommand": "spago build --no-install --purs-args '--json-errors'",
"purescript.editorMode": true,

Each module is structured more or less as a series of functions to implement.

Running yarn test will run the tests for the project and running yarn test:watch will make sure that the tests are re-run when files change.

If you want to run only the tests for a certain file, run yarn test -- -a '-t simple' where "simple" can also be "maybe", "list" or "recursion" as the tests are split up into the modules that they cover.

If you want to run only the tests for a certain file in watch mode, run yarn test:watch -- -a '-t simple'.

While it's possible to open any file in the repository and start working, the recommended order is as follows:

1. Simple.purs - This introduces the language of PureScript by way of simple functions that you may recognize from other languages.
2. Bool.purs - Introduces the concept of pattern matching by way of a series of functions operating on boolean values to produce new boolean values.
3. Maybe.purs - Introduces the idea of a data type that either contains a value of some type or contains nothing. This is a type-safe alternative to null.
4. Recursion.purs - Introduces non-list based recursion as a concept, emphasizing the idea slicing up work into discrete units.
5. List.purs - Introduces functions relating to linked lists and how to work with them in a functional context.