# Installing Elixir: IEx, Mix and Hex — Elixir & Phoenix

Source: https://www.geekswithgeeks.com/en/elixir-phoenix/f-setup

> Install Elixir and Erlang, explore in IEx and create Mix projects.

## The Elixir toolchain

Elixir needs **Erlang/OTP** underneath. Install both with a version manager such as **asdf** or **mise** (pinning versions in `.tool-versions`), or with your OS package manager; on Windows there are installers. **IEx** (Interactive Elixir) is the REPL: `iex` starts it, `h Enum.map` shows documentation, `i value` inspects a value, and `iex -S mix` loads your project. **Mix** is the build tool: `mix new shop` creates a project with `mix.exs` (project configuration and dependencies), `lib/` for code and `test/` for tests; `mix compile`, `mix test`, `mix format` and `mix run` are everyday commands. Use `mix new shop --sup` to generate an application with a supervision tree. **Hex** (hex.pm) is the package registry: add dependencies to `deps` in `mix.exs` with version requirements like `{:jason, "~> 1.4"}` and run `mix deps.get`; `mix.lock` pins exact versions. Documentation for every package is on **HexDocs**. For editors, use an Elixir language server (such as ElixirLS or the newer Expert project) in VS Code, Neovim or similar. **Livebook** provides interactive notebooks for learning and data work.

## Creating and exploring a Mix project

Generate a supervised app, add a dependency and open IEx.

```bash
mise use erlang@27 elixir@1.18    # or: asdf install, using a .tool-versions file
elixir --version

mix new shop --sup                 # project with an application and supervisor
cd shop

# mix.exs (excerpt)
# defp deps do
#   [
#     {:jason, "~> 1.4"},
#     {:credo, "~> 1.7", only: [:dev, :test], runtime: false}
#   ]
# end

mix deps.get                       # fetch from Hex, writes mix.lock
mix test                           # run ExUnit tests
mix format                         # format all code
iex -S mix                         # IEx with the project loaded

# inside IEx:
#   h Enum.map         documentation
#   i "hello"           what is this value?
#   recompile()         reload changed code
```

## A workshop with a librarian

Mix is your workshop bench where projects are built and tested; Hex is the librarian who fetches the right version of every tool you ask for; IEx is the scratch pad on the side for trying ideas.

**Quiz:** What does `mix new shop --sup` add compared with plain `mix new shop`?

- [ ] A web server
- [ ] A database
- [ ] Static types
- [x] An application module with a supervision tree

*Answer:* An application module with a supervision tree. The --sup flag generates an Application that starts a supervisor.