Haskell Blockchain

About

This is an experimental project for me to learn Haskell a little bit better.

The use case is a very simple blockchain along with a web server for interacting with it along with Postgres interactivity.

Directory Structure

Here's a suggested directory structure:

haskell-blockchain/
├── app/
│   └── Main.hs
├── src/
│   └── Blockchain.hs
|   └── Web.hs
├── test/
│   └── Spec.hs
├── haskell-blockchain.cabal
├── stack.yaml
└── Setup.hs

app/Main.hs: The entry point of your application. It will import your blockchain module from src/ and run the main application logic. src/Blockchain.hs: Contains the blockchain logic, including data structures and functions for creating and manipulating the blockchain. src/Web.hs: Contains the REST Web API for interacting with our blockchain. test/Spec.hs: For any tests you want to write using a framework like Hspec. haskell-blockchain.cabal: Cabal file describing your application's properties, dependencies, and build information. stack.yaml: (Optional) If you're using Stack, this file will configure the project's stack tool settings. Setup.hs: Used by Cabal, typically a boilerplate file for simple projects.

Initializing the Project (Done)

You can initialize the project using either Cabal or Stack. These tools help manage dependencies, build processes, and package configurations.

Using Cabal

Install GHC and Cabal if you haven't already. Navigate to your project directory and run: cabal init

Follow the interactive prompts to set up your project. You can choose the executable type when prompted, as this project is an application. Add your dependencies to the generated .cabal file. For this project, you might need base, time, and cryptonite for cryptographic functions.

Using Stack

Install Stack if you haven't already. Navigate to project directory and run: stack new haskell-blockchain simple

This command creates a new project using the "simple" template. Update the stack.yaml and haskell-blockchain.cabal files with your project's dependencies.

Building and Running the Project

Using Cabal

Build project: cabal build

Run project: cabal run

Using Stack

Build project: stack build

Run project: stack exec haskell-blockchain-exe stack run

Replace haskell-blockchain-exe with the name of your executable defined in the Cabal file if you are using a different name.

Assorted Notes

Cautionary Tales

Dependency conflicts can be particularly brutal with Haskell.

After a whole lot of trial and error (mostly error) with stack, I would up switching to cabal.

Even with cabal, I went through a few learning lessons to get things off the ground.

One thing to take note of: The build-depends sections of both the library and executable have to match. I spent way too much time trying to figure out why some of my dependencies simply were not being recognized.

Also, take note of some of the CLI commands in the following section in case you need to use a specific version of GHC, etc.

Some CLI Commands

stack exec -- ghc-pkg list

stack setup --resolver ghc-8.8.4

$env:GHC_PACKAGE_PATH = "C:\Users\Darren\AppData\Local\Programs\stack\x86_64-windows\ghc-9.10.1\lib\package.conf.d"
echo $env:GHC_PACKAGE_PATH

#### To unset:
$env:GHC_PACKAGE_PATH=""

stack exec -- cabal init

ghcup install ghc 8.8.4
ghcup set ghc 8.8.4
$env:PATH = "C:\ghcup\bin;" + $env:PATH

Testing

cabal repl :l src/Database.hs :t Envy.envMaybe "PG_PORT"