OCaml

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### Start OCaml UTop Toplevel

Source: https://ocaml.org/docs/installing-ocaml

This command launches the UTop interactive toplevel (REPL) for OCaml. It allows users to execute OCaml expressions directly and interact with the language, confirming the UTop and OCaml versions upon startup.

```Shell
utop
```

--------------------------------

### Install opam on Windows with WinGet

Source: https://ocaml.org/docs/installing-ocaml

This PowerShell command installs Git and opam on Windows using the WinGet package manager. It is presented as the easiest method for Windows users.

```PowerShell
winget install Git.Git OCaml.opam
```

--------------------------------

### Install latest opam via binary distribution script (Unix/macOS)

Source: https://ocaml.org/docs/installing-ocaml

This shell script installs the latest version of opam on Unix-like systems and macOS by downloading and executing an installation script. This method ensures you get the most recent release.

```Bash
bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh)"
```

--------------------------------

### Install latest opam via binary distribution script (PowerShell)

Source: https://ocaml.org/docs/installing-ocaml

This PowerShell command installs the latest version of opam on Windows, equivalent to the binary distribution script for Unix. It uses Invoke-RestMethod to fetch and execute the installer.

```PowerShell
Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) }"
```

--------------------------------

### Install Opam and Git on Windows using winget

Source: https://ocaml.org/docs/ocaml-on-windows

This command uses `winget` to install both Git and Opam on a Windows system. Git is a prerequisite for Opam, and `winget` provides a convenient way to manage these installations.

```Shell
winget install Git.Git OCaml.opam
```

--------------------------------

### Start OCaml UTop Interactive Toplevel

Source: https://ocaml.org/docs/get-started

This command launches the UTop interactive toplevel (REPL) for OCaml, allowing users to execute OCaml expressions directly. It's used to verify the successful installation of UTop.

```Shell
utop
```

--------------------------------

### Install opam on Windows with WinGet

Source: https://ocaml.org/docs/get-started

This command installs Git and opam on Windows using the WinGet package manager. WinGet simplifies software installation on Windows from the command line.

```powershell
winget install Git.Git OCaml.opam
```

--------------------------------

### OCaml Windows Installation Support Tiers

Source: https://ocaml.org/docs/ocaml-on-windows

This table outlines the support tiers for different OCaml versions and environments when installing OCaml on Windows. It categorizes support levels from fully supported (Tier 1) to user-supported (Tier 3) across various tools like opam, Diskuv OCaml, WSL2, and Docker, helping users choose the most suitable installation method.

```text
╭──────────────────────────────────────────────────────────────────────────╮
│ Tier   │ OCaml Version and Environment   │ Support                       │
│ ------ │ ------------------------------- │ ----------------------------- │
│ Tier 1 │ OCaml 5.x with Opam 2.2+        │ Full support.                 │
│ Tier 2 │ 4.14.x with Diskuv OCaml        │ Supported on select versions. │
│ Tier 3 │ 5.x with WSL2                   │ User supported.               │
│ Tier 3 │ 5.x with Docker                 │ User supported.               │
╰──────────────────────────────────────────────────────────────────────────╯
```

--------------------------------

### Verify Diskuv OCaml Installation

Source: https://ocaml.org/docs/ocaml-on-windows

Use these shell commands in PowerShell or Command Prompt to confirm that Diskuv OCaml is correctly installed and its executables are accessible, displaying the OCaml version.

```Shell
$ where.exe ocaml
C:\Users\frank\AppData\Local\Programs\DiskuvOCaml\usr\bin\ocaml.exe

$ ocaml -version
The OCaml toplevel, version 4.14.0
```

--------------------------------

### Install latest opam via binary distribution script (Windows PowerShell)

Source: https://ocaml.org/docs/get-started

This PowerShell command downloads and executes an installation script for the latest opam binary distribution on Windows. It uses `Invoke-RestMethod` to fetch the script and `Invoke-Expression` to run it.

```powershell
Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) }"
```

--------------------------------

### Example OCaml Executable Stanza for Dune

Source: https://ocaml.org/docs/running-executables-and-tests-with-dune

This is a concrete example of a Dune executable stanza. It defines an executable named 'main' internally, which will be installed as 'my-app'. It links no additional libraries in this specific example, demonstrating a minimal configuration.

```Dune Configuration
(executable
 (name main)
 (public_name my-app)
 (libraries))
```

--------------------------------

### Initialize opam

Source: https://ocaml.org/docs/installing-ocaml

This command initializes opam after installation, setting up the necessary environment. This process may take a few minutes to complete.

```Shell
opam init -y
```

--------------------------------

### Install OCaml Platform Tools using opam

Source: https://ocaml.org/docs/installing-ocaml

This command installs essential OCaml development tools such as ocaml-lsp-server, odoc, ocamlformat, and utop using the opam package manager. These tools provide features like language server support, documentation generation, code formatting, and an interactive REPL.

```Shell
opam install ocaml-lsp-server odoc ocamlformat utop
```

--------------------------------

### Install latest opam via binary distribution script (Unix/macOS)

Source: https://ocaml.org/docs/get-started

This command downloads and executes an installation script for the latest opam binary distribution on Unix-like systems and macOS. It uses `curl` to fetch the script and `bash` to run it, potentially requiring `sudo` internally.

```bash
bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh)"
```

--------------------------------

### Install opam on Debian/Ubuntu Linux

Source: https://ocaml.org/docs/installing-ocaml

This command installs opam on Debian or Ubuntu Linux distributions using the apt-get package manager. Superuser privileges are required for this operation.

```Shell
sudo apt-get install opam
```

--------------------------------

### Verify OCaml Installation and Run Interactive Toplevel

Source: https://ocaml.org/docs/ocaml-on-windows

This snippet demonstrates how to check the OCaml compiler version using a shell command and then launch the interactive OCaml toplevel. It includes a simple "Hello World" program execution within the toplevel to confirm a functional OCaml environment.

```Shell
ocaml --version
The OCaml toplevel, version 5.2.0
```

```OCaml
ocaml
OCaml version 5.2.0
Enter #help;; for help.

# print_endline "Hello OCamleers!!";;
Hello OCamleers!!
- : unit = ()
#
```

--------------------------------

### Configure Merlin User Setup via OPAM

Source: https://ocaml.org/docs/set-up-editor

Shell command to run Merlin's user setup process. This command typically prints instructions on how to link Merlin with various editors, ensuring proper integration after installation.

```Shell
opam user-setup install
```

--------------------------------

### Install opam on Arch Linux

Source: https://ocaml.org/docs/installing-ocaml

This command installs opam on Arch Linux using the pacman package manager. It requires superuser privileges to execute.

```Shell
sudo pacman -S opam
```

--------------------------------

### Compile and Run OCaml File Manipulation Example

Source: https://ocaml.org/docs/file-manipulation

This shell snippet provides commands to compile the OCaml file manipulation example using `ocamlopt` and then execute the resulting binary to observe its output.

```Shell
$ ocamlopt -o file_manip file_manip.ml
$ ./file_manip
Hello!
```

--------------------------------

### Install opam on Debian/Ubuntu Linux

Source: https://ocaml.org/docs/get-started

This command installs the opam package manager on Debian or Ubuntu Linux distributions using `apt-get`. It requires superuser privileges.

```bash
sudo apt-get install opam
```

--------------------------------

### Verify Opam Installation Version

Source: https://ocaml.org/docs/ocaml-on-windows

This command checks the installed version of Opam. It confirms that Opam has been successfully added to the system's PATH and is executable.

```Shell
opam --version
2.2.1
```

--------------------------------

### Install opam on macOS with MacPorts

Source: https://ocaml.org/docs/installing-ocaml

This command installs the opam package manager on macOS using MacPorts. It provides an alternative installation method for Mac users.

```Shell
port install opam
```

--------------------------------

### Install opam on Debian/Ubuntu without OCaml dependencies

Source: https://ocaml.org/docs/installing-ocaml

This command installs only opam on Debian or Ubuntu, preventing the installation of recommended OCaml compiler dependencies. Use this if you only need opam and want to manage OCaml separately.

```Shell
sudo apt-get install --no-install-recommends opam
```

--------------------------------

### Install opam on Debian/Ubuntu without OCaml recommends

Source: https://ocaml.org/docs/get-started

This command installs only the opam package on Debian or Ubuntu, explicitly avoiding the installation of recommended dependencies like the OCaml compiler. This is useful if you only need opam and not the compiler immediately.

```bash
sudo apt-get install --no-install-recommends opam
```

--------------------------------

### Install opam on Arch Linux

Source: https://ocaml.org/docs/get-started

This command installs the opam package manager on Arch Linux using `pacman`. It requires superuser privileges.

```bash
sudo pacman -S opam
```

--------------------------------

### Install Merlin for OCaml Editor Integration

Source: https://ocaml.org/docs/ocaml-on-windows

Install the Merlin system, an OCaml language server, using the opam package manager to enable advanced features like auto-completion and type checking in compatible editors.

```Shell
opam install merlin
```

--------------------------------

### Install opam on macOS with Homebrew

Source: https://ocaml.org/docs/installing-ocaml

This command installs the opam package manager on macOS using the Homebrew package manager. It's a common method for adding opam to your system.

```Shell
brew install opam
```

--------------------------------

### Install opam on macOS with Homebrew

Source: https://ocaml.org/docs/get-started

This command installs the opam package manager on macOS using Homebrew. Homebrew is a popular package manager for macOS that simplifies software installation.

```bash
brew install opam
```

--------------------------------

### Install OCaml Platform Tools using opam

Source: https://ocaml.org/docs/get-started

This command installs essential OCaml development tools including the language server, documentation generator, code formatter, and interactive toplevel, using the opam package manager. It ensures a complete OCaml development environment.

```Shell
opam install ocaml-lsp-server odoc ocamlformat utop
```

--------------------------------

### Initialize opam after installation

Source: https://ocaml.org/docs/get-started

This command initializes opam after its installation, setting up the necessary environment. The `-y` flag automatically confirms prompts, making the process non-interactive. This step is crucial for opam to function correctly.

```bash
opam init -y
```

--------------------------------

### OCaml List Initialization Examples

Source: https://ocaml.org/docs/tour-of-ocaml

Provides various examples of list creation in OCaml, including empty lists, lists of integers, lists of booleans, and nested lists. These examples showcase OCaml's strong typing and how lists maintain a consistent element type.

```OCaml
# [];;
# [1; 2; 3];;
# [false; false; true];;
# [[1; 2]; [3]; [4; 5; 6]];;
```

--------------------------------

### Install opam on macOS with MacPorts

Source: https://ocaml.org/docs/get-started

This command installs the opam package manager on macOS using MacPorts. MacPorts is another package management system for macOS, providing a comprehensive collection of open-source software.

```bash
port install opam
```

--------------------------------

### Example Running OCaml Executable with Dune

Source: https://ocaml.org/docs/running-executables-and-tests-with-dune

A practical example demonstrating how to run a specific OCaml executable named 'main' or its public alias 'my-app' using the `dune exec` command. This illustrates the typical command line usage for executing Dune-built applications.

```Shell
dune exec bin/main.exe
dune exec my-app
```

--------------------------------

### Create Project Directory

Source: https://ocaml.org/docs/libraries-dune

Shell commands to create the root directory for the OCaml project and navigate into it. This is the initial step for setting up the project workspace.

```Shell
mkdir mixtli; cd mixtli
```

--------------------------------

### Run OCaml UTop Toplevel

Source: https://ocaml.org/docs/toplevel-introduction

Execute the `utop` command in the terminal to start the OCaml Read-Eval-Print-Loop (REPL). This command launches the UTop environment, displaying a welcome message and a prompt for user input.

```Shell
$ utop
────────┬─────────────────────────────────────────────────────────────┬─────────
        │ Welcome to utop version 2.12.1 (using OCaml version 5.0.0)! │
        └─────────────────────────────────────────────────────────────┘

Type #utop_help for help about using utop.

─( 17:00:09 )─< command 0 >──────────────────────────────────────{ counter: 0 }─
utop #
```

--------------------------------

### Set opam environment variables (Windows Command Prompt)

Source: https://ocaml.org/docs/installing-ocaml

This command sets opam environment variables in the Windows Command Prompt. It parses the output of 'opam env' and executes the resulting commands.

```Command Prompt
for /f \"tokens=*\" %i in ('opam env') do @%i
```

--------------------------------

### Compile and Run OCaml Arg Module Example

Source: https://ocaml.org/docs/cli-arguments

This section provides examples of compiling the OCaml program and running it with various command-line arguments. It demonstrates successful argument parsing, how the program handles unknown options by displaying an error and usage message, and how to request the help output.

```Shell
$ ocamlopt -o append append.ml
$ ./append -verbose one.txt two.txt -o three.txt
$ ./append one.txt two.txt
$ ./append -quiet
./append: unknown option '-quiet'.
append [-verbose] <file1> [<file2>] ... -o <output>
  -verbose Output debug information
  -o Set output file name
  -help  Display this list of options
  --help  Display this list of options
[2]
$ ./append -help
append [-verbose] <file1> [<file2>] ... -o <output>
  -verbose Output debug information
  -o Set output file name
  -help  Display this list of options
  --help  Display this list of options
```

--------------------------------

### Install Project Dependencies with opam 2.0.X

Source: https://ocaml.org/docs/managing-dependencies

This command sequence installs project dependencies in a local opam switch for opam versions 2.0.X. It handles external system dependencies, then installs project dependencies, including test and documentation dependencies.

```Shell
opam pin add -n .
opam depext -i <packages>
opam install . --deps-only --with-test --with-doc
```

--------------------------------

### OCaml File Write and Read Example

Source: https://ocaml.org/docs/file-manipulation

This OCaml snippet demonstrates how to write a string to a file and then read the first line back. It showcases the use of `open_out`, `Printf.fprintf`, `close_out`, `open_in`, `input_line`, `print_endline`, and proper error handling with channel closing.

```OCaml
let file = "example.dat"
let message = "Hello!"

let () =
  (* Write message to file *)
  let oc = open_out file in
  (* create or truncate file, return channel *)
  Printf.fprintf oc "%s\n" message;
  (* write something *)
  close_out oc;

  (* flush and close the channel *)

  (* Read file and display the first line *)
  let ic = open_in file in
  try
    let line = input_line ic in
    (* read line, discard \n *)
    print_endline line;
    (* write the result to stdout *)
    flush stdout;
    (* write on the underlying device now *)
    close_in ic
    (* close the input channel *)
  with e ->
    (* some unexpected exception occurs *)
    close_in_noerr ic;
    (* emergency closing *)
    raise e

(* exit with error: files are closed but channels are not flushed *)

(* normal exit: all channels are flushed and closed *)
```

--------------------------------

### Install OCaml LSP and Formatter with opam

Source: https://ocaml.org/docs/set-up-editor

This command installs the `ocaml-lsp-server` and `ocamlformat` packages using the `opam` package manager. These tools are essential for enabling advanced OCaml language features and code formatting in your editor, particularly for Visual Studio Code.

```Shell
opam install ocaml-lsp-server ocamlformat
```

--------------------------------

### Install Project Dependencies in a Global opam Switch

Source: https://ocaml.org/docs/managing-dependencies

This command sequence sets a specified global opam switch and then installs project dependencies within it, including test and documentation dependencies.

```Shell
opam switch set <switch_name>
opam install . --deps-only --with-test --with-doc
```

--------------------------------

### Build and Run OCaml Project with Dune

Source: https://ocaml.org/docs/bootstrapping-a-dune-project

After initializing a project, navigate into its directory. This command then uses `dune exec` to build and run the main executable of the OCaml project. It demonstrates successful execution of the 'Hello, world!' program.

```Shell
$ cd hello_world
$ opam exec -- dune exec bin/main.exe
Hello, world!
```

--------------------------------

### Initialize New OCaml Project with Dune

Source: https://ocaml.org/docs/tools

This command uses `dune init project` to create a new OCaml project named 'hello_world'. It leverages `opam exec` to ensure the command runs within the correct OCaml environment. The output confirms successful initialization.

```Shell
$ opam exec -- dune init project hello_world
Success: initialized project component named hello_world
```

--------------------------------

### Install ppx_deriving OCaml Package

Source: https://ocaml.org/docs/your-first-program

This command installs the `ppx_deriving` package using opam, which is an OCaml preprocessor used for automatically generating code, such as `show` functions for type serialization.

```Shell
opam install ppx_deriving
```

--------------------------------

### Build and Run OCaml Project with Dune

Source: https://ocaml.org/docs/tools

After initializing a project, navigate into its directory. This command then uses `opam exec` and `dune exec` to build and run the main executable of the 'hello_world' project. The output shows the program's execution.

```Shell
$ cd hello_world
$ opam exec -- dune exec bin/main.exe
Hello, world!
```

--------------------------------

### OCaml Partial Application Example

Source: https://ocaml.org/docs/tour-of-ocaml

Demonstrates partial application in OCaml, where a function is called with fewer arguments than it expects, returning a new function that takes the remaining arguments. Shows the initial function call, the partial application, and the subsequent call to the new function.

```OCaml
# cat "ha" "ha";;
- : string = "ha ha"
```

```OCaml
# let cat_hi = cat "hi";;
val cat_hi : string -> string = <fun>
```

```OCaml
# cat_hi "friend";;
- : string = "hi friend"
```

--------------------------------

### Install Project Dependencies with opam 2.1.X

Source: https://ocaml.org/docs/managing-dependencies

This command installs project dependencies in a local opam switch for opam versions 2.1.X. It automatically handles system dependencies and includes test and documentation dependencies.

```Shell
opam install . --deps-only --with-test --with-doc
```

--------------------------------

### Create OCaml Project Directory

Source: https://ocaml.org/docs/functors

This shell command creates a new directory named 'funkt' and navigates into it, serving as the initial step for setting up an OCaml project.

```shell
mkdir funkt; cd funkt
```

--------------------------------

### List Available OCaml Compiler Versions

Source: https://ocaml.org/docs/install-a-specific-ocaml-compiler-version

This command retrieves and displays a list of all OCaml compiler versions that are available for installation from the currently configured opam repositories. It helps in identifying which versions can be used to create new switches.

```shell
opam switch list-available
```

--------------------------------

### Initialize New OCaml Project with Dune

Source: https://ocaml.org/docs/bootstrapping-a-dune-project

This command uses `dune init project` to create a new OCaml project named 'hello_world'. It bootstraps the project structure, making it ready for development. Requires `dune` to be installed and `opam` for execution.

```Shell
$ opam exec -- dune init project hello_world
Success: initialized project component named hello_world
```

--------------------------------

### Install OCaml LSP Server and OCamlformat via OPAM

Source: https://ocaml.org/docs/set-up-editor

Shell command to install 'ocaml-lsp-server' and 'ocamlformat' using the OPAM package manager. These tools are essential for providing Language Server Protocol features and code formatting for OCaml projects.

```Shell
opam install ocaml-lsp-server ocamlformat
```

--------------------------------

### Run Basic Arithmetic in OCaml Playground

Source: https://ocaml.org/docs/ocaml-playground

Demonstrates how to perform a simple addition operation (2+3) in the OCaml Playground editor and observe the integer output of '5'. This is a fundamental example for new users.

```OCaml
2+3
```

--------------------------------

### OCaml Obfuscated Code Example

Source: https://ocaml.org/docs/guidelines

An extreme example of highly unreadable and overly complicated OCaml code, demonstrating multiple anti-patterns like mixing computations and side effects, nested anonymous functions, and complex `let in` bindings. This code achieves a simple 'Hello world!' output in an unnecessarily convoluted manner.

```OCaml
(fun u -> print_string "world"; print_string u)
  (let temp = print_string "Hello"; "!" in
   ((fun x -> print_string x; flush stdout) " ";
    temp));;
```

--------------------------------

### Install MSVC C Compiler for Opam

Source: https://ocaml.org/docs/ocaml-on-windows

This `opam` command installs the Microsoft Visual C++ compiler as an alternative C compiler for Opam switches. By default, Opam uses `mingw`, but this allows users to specify `msvc` for their OCaml projects.

```Shell
opam install system-msvc
```

--------------------------------

### Configure Vim PATH for OCaml Merlin

Source: https://ocaml.org/docs/ocaml-on-windows

This Vimscript command modifies the Vim PATH environment variable to include the directory where opam installs binaries, ensuring that Merlin can be located and used by Vim.

```Vimscript
let $PATH .= ";".substitute(system('opam config var bin'),'\n$','','''')
```

--------------------------------

### MiniGtk Basic Window and Label Creation (OCaml)

Source: https://ocaml.org/docs/calling-c-libraries

Demonstrates how to create a window and a label using the MiniGtk single-layered object-oriented API in OCaml. It shows object instantiation, adding widgets, and calling the main event loop.

```OCaml
let win = new Gtk.window ~title:"My window" ();;
let lbl = new Gtk.label ~text:"Hello" ();;
win#add lbl;;

let () =
  Gtk.main ()

```

--------------------------------

### Simple OCaml Hello World Program

Source: https://ocaml.org/docs/using-the-ocaml-compiler-toolchain

This is a basic OCaml program that prints "Hello Dune!" to the console. It serves as a minimal example for testing the Dune build system.

```OCaml
let () = print_endline "Hello Dune!"
```

--------------------------------

### Install Project Dependencies with opam --deps-only

Source: https://ocaml.org/docs/managing-dependencies

This command installs all dependencies specified in the current project's .opam file, including any newly added ones. It's a crucial step after modifying dependency declarations to ensure all required packages are fetched.

```Shell
opam install . --deps-only
```

--------------------------------

### OCaml Optional Parameter Usage Examples for String Substring

Source: https://ocaml.org/docs/labels

Shows various ways to call the `sub` function, demonstrating how optional parameters `len` and `pos` affect the output when provided or omitted. These examples highlight the flexibility of optional arguments in OCaml.

```OCaml
# sub ~len:5 ~pos:2 "immutability";;
- : string = "mutab"

# sub "immutability" ~pos:7 ;;
- : string = "ility"

# sub ~len:2 "immutability";;
- : string = "im"

# sub "immutability";;
- : string = "immutability"
```

--------------------------------

### Initialize OCaml Project with Dune

Source: https://ocaml.org/docs/your-first-program

This command initializes a new OCaml project named 'hello' using Dune. It sets up the basic directory structure and configuration files required for an OCaml application, ensuring a proper starting point for development.

```Shell
opam exec -- dune init proj hello
```

--------------------------------

### Set opam environment variables (Unix)

Source: https://ocaml.org/docs/installing-ocaml

This command sets the necessary environment variables for opam on Unix-like systems after initialization. It integrates opam into your current shell session.

```Shell
eval $(opam env)
```

--------------------------------

### Dune: Initial Configuration for Wrapped OCaml Library

Source: https://ocaml.org/docs/compiler-frontend

This Dune configuration defines a library named 'hello' that includes modules 'a' and 'b'. It also sets up an executable 'test' that links against the 'hello' library, demonstrating the basic setup for a wrapped OCaml library.

```Dune
(library
  (name hello)
  (modules a b))
(executable
  (name test)
  (libraries hello)
  (modules test))
```

--------------------------------

### Initialize opam in Docker without sandboxing

Source: https://ocaml.org/docs/installing-ocaml

This command initializes opam inside a Docker container, disabling sandboxing. This is necessary unless the Docker container is run in privileged mode.

```Shell
opam init --disable-sandboxing -y
```

--------------------------------

### Initialize opam in Docker without sandboxing

Source: https://ocaml.org/docs/get-started

This command initializes opam inside a Docker container, explicitly disabling sandboxing. This is necessary when running opam in a non-privileged Docker container to avoid permission issues.

```bash
opam init --disable-sandboxing -y
```

--------------------------------

### Set opam environment variables (Windows PowerShell)

Source: https://ocaml.org/docs/installing-ocaml

This command sets opam environment variables in PowerShell. It processes the output of 'opam env' and invokes each line as an expression to configure the environment.

```PowerShell
(& opam env) -split '\r?\n' | ForEach-Object { Invoke-Expression $_ }
```

--------------------------------

### OCaml Comment Syntax and Usage

Source: https://ocaml.org/docs/tour-of-ocaml

Demonstrates how to write single-line and nested comments in OCaml. Comments start with `(*` and end with `*)` and can be placed anywhere whitespace is allowed. The example also shows a comment within an expression and its evaluation in the toplevel.

```OCaml
(* Here is a comment *)
(* Outside of the nested comment is still a comment. (* Here is a nested comment *) Outside of the nested comment again. *)
# 50 + (* A comment in between parts of an expression *) 50;;
- : int = 100
```

--------------------------------

### Dune Execution with OCAMLRUNPARAM for Backtrace

Source: https://ocaml.org/docs/debugging

This example demonstrates how to combine the 'OCAMLRUNPARAM=b' environment variable with 'dune exec' to get a detailed backtrace for uncaught exceptions in OCaml projects managed by Dune. This is crucial for debugging Dune-built applications.

```Shell
OCAMLRUNPARAM=b dune exec ./uncaught.exe
Fatal error: exception Not_found
Raised at Stdlib__List.assoc in file "list.ml", line 191, characters 10-25
Called from Dune__exe__Uncaught.find_address in file "uncaught.ml" (inlined), line 3, characters 24-42
Called from Dune__exe__Uncaught in file "uncaught.ml", line 8, characters 15-37
```

--------------------------------

### Update Opam Environment in CMD

Source: https://ocaml.org/docs/ocaml-on-windows

This command updates the current command prompt environment with Opam's settings for the default switch. It's necessary after `opam init` to ensure Opam commands are correctly recognized and available.

```CMD
for /f "tokens=*" %i in ('opam env --switch=default') do @%i
```

--------------------------------

### Execute OCaml Expression in UTop

Source: https://ocaml.org/docs/installing-ocaml

This snippet demonstrates how to execute a simple OCaml arithmetic expression within the UTop toplevel. It shows the input expression and the resulting type and value, confirming the OCaml environment is functional.

```OCaml
# 21 * 2;;
```

--------------------------------

### OCaml: Manual 'hello.mli' for Top-Level Module Documentation

Source: https://ocaml.org/docs/compiler-frontend

This OCaml interface file ('hello.mli') provides documentation for the submodules 'A' and 'B' within the 'Hello' library. It demonstrates how to add rich documentation strings and type signatures for the exposed values, enhancing the usability and clarity of the wrapped library.

```OCaml
(** Documentation for module A *)
module A : sig
  (** [v] is Hello *)
  val v : string
end

(** Documentation for module B *)
module B : sig
  (** [w] is 42 *)
  val w : int
end
```

--------------------------------

### Update Opam Environment in PowerShell

Source: https://ocaml.org/docs/ocaml-on-windows

This PowerShell command updates the current shell environment with Opam's settings for the default switch. It parses the output of `opam env` and applies the necessary environment variables for Opam commands to function correctly.

```PowerShell
(& opam env --switch=default) -split '\r?\n' | ForEach-Object { Invoke-Expression $_ }
```

--------------------------------

### Define example list of names and an uncurried `reveal` function in OCaml

Source: https://ocaml.org/docs/higher-order-functions

This OCaml snippet defines a list of strings `names` and an uncurried function `reveal` that takes a tuple `(title, name)` and prints a formatted string. This setup is used to demonstrate the application of currying.

```OCaml
let names = [
  "Sabine";
  "Xavier";
  "Louis";
]
;;

let reveal (title, name) =
  Printf.printf "But it was %s, %s!\n" title name
;;

```

--------------------------------

### Install OCaml TSan Switch with OPAM

Source: https://ocaml.org/docs/debugging

This command creates a new OPAM switch for OCaml version 5.2.0, specifically enabling the Thread Sanitizer (TSan) option. This setup is crucial for configuring the OCaml environment to detect data races in multicore applications.

```Shell
opam switch create 5.2.0+tsan ocaml-variants.5.2.0+options ocaml-option-tsan
```

--------------------------------

### Create New OCaml Executable with Dune

Source: https://ocaml.org/docs/tools

This command uses `dune init exec` to create a new OCaml executable named 'my_bin' at the specified path within the current project. It runs within the appropriate OCaml environment using `opam exec`. The output confirms successful executable initialization.

```Shell
$ opam exec -- dune init exec my_bin ./path/to/my_bin
Success: initialized executable component named my_bin
```

--------------------------------

### Dune Project Module Structure Description

Source: https://ocaml.org/docs/libraries-dune

The output of `dune describe` provides a detailed S-expression representation of the project's internal structure as understood by Dune. It lists build contexts, executables, and the modules (Wmo, Cloud) with their associated implementation and interface files.

```Dune
((root /home/cuihtlauac/caml/mixtli-dune)
 (build_context _build/default)
 (executables
  ((names (cloud))
   (requires ())
   (modules
    (((name Wmo)
      (impl (_build/default/wmo.ml))
      (intf ())
      (cmt (_build/default/.cloud.eobjs/byte/wmo.cmt))
      (cmti ()))
```

--------------------------------

### Two-Phase Deconstruction of OCaml Record and Nested Tuple

Source: https://ocaml.org/docs/values-and-functions

This example demonstrates a two-step approach to deconstruct an OCaml record with a nested tuple. First, the record fields, including the 'contact' tuple, are extracted. Then, the 'contact' tuple itself is deconstructed to get 'email' and 'phone', making 'contact' available at the top-level scope.

```OCaml
(* Step 1: deconstruct all record fields *)
# let { name; street; city; zip; contact } = jane;;
val name : string = "Jane Doe"
val street : string = "123 Elm St"
val city : string = "Springfield"
val zip : int = 12345
val contact : string * int = ("jane@example.com", 1234567890)
```

```OCaml
(* Step 2: deconstruct the tuple *)
# let ( email, phone ) = contact;;
val email : string = "jane@example.com"
val phone : int = 1234567890
```

--------------------------------

### List opam switches

Source: https://ocaml.org/docs/opam-switch-introduction

This command displays all opam switches configured on the system, showing their name, associated OCaml compiler version, and a brief description. It helps users see existing isolated OCaml environments.

```Shell
$ opam switch list
#   switch   compiler      description
->  default  ocaml.4.13.1  default
```

--------------------------------

### Applying Let-In and Multi-line Indentation to OCaml List Operators

Source: https://ocaml.org/docs/guidelines

This OCaml example extends the `let in` and multi-line operator indentation guidelines to list concatenation (`::`) operations. It shows how to bind a large expression and then continue a list construction across multiple lines, with the `::` operator starting the new line for clarity.

```OCaml
let u =
  "large
  expression" in
x :: y
:: z + 1 :: t :: u
```

--------------------------------

### Complete OCaml Command-Line Parser Program

Source: https://ocaml.org/docs/cli-arguments

This snippet presents the full OCaml program that utilizes the `Arg` module to parse command-line arguments. It combines the usage message, reference initializations, anonymous function, specification list, and the `Arg.parse` call into a single, runnable example, demonstrating a complete command-line interface setup.

```OCaml
let usage_msg = "append [-verbose] <file1> [<file2>] ... -o <output>"

let verbose = ref false

let input_files = ref []

let output_file = ref ""

let anon_fun filename =
  input_files := filename :: !input_files

let speclist =
  [("-verbose", Arg.Set verbose, "Output debug information");
   ("-o", Arg.Set_string output_file, "Set output file name")]

let () =
  Arg.parse speclist anon_fun usage_msg;
  (* Main functionality here *)
```

--------------------------------

### Create New OCaml Executable with Dune

Source: https://ocaml.org/docs/bootstrapping-a-dune-project

This command uses `dune init exec` to create a new OCaml executable component named 'my_bin' within the current project. It prepares the directory and files for a new standalone executable. The path indicates the location for the executable's source.

```Shell
$ opam exec -- dune init exec my_bin ./path/to/my_bin
Success: initialized executable component named my_bin
```

--------------------------------

### Dune Executable Configuration (Initial)

Source: https://ocaml.org/docs/libraries-dune

This `dune` file configures the build system to create an executable program. It specifies the OCaml source file (`cloud.ml`) that contains the main entry point and defines the public name (`nube`) for the compiled executable.

```Dune
(executable
  (name cloud)
  (public_name nube))
```

--------------------------------

### Create C Main Entry Point for OCaml Embedding

Source: https://ocaml.org/docs/compiler-backend

A C program that serves as the main entry point for an application embedding OCaml bytecode. It initializes the OCaml runtime using `caml_startup` and demonstrates interaction before and after OCaml execution.

```C
#include <stdio.h>
#include <caml/alloc.h>
#include <caml/mlvalues.h>
#include <caml/memory.h>
#include <caml/callback.h>

int
main (int argc, char **argv)
{
  printf("Before calling OCaml\n");
  fflush(stdout);
  caml_startup (argv);
  printf("After calling OCaml\n");
  return 0;
}
```

--------------------------------

### OCaml Cloud Module Main Program

Source: https://ocaml.org/docs/libraries-dune

The `cloud.ml` file serves as the main program for the executable. It imports and utilizes the `Wmo` module to print the `nimbus` values from its `Stratus` and `Cumulus` submodules to the console.

```OCaml
let () =
  Wmo.Stratus.nimbus |> print_endline;
  Wmo.Cumulus.nimbus |> print_endline
```

--------------------------------

### Create New OCaml Library with Dune

Source: https://ocaml.org/docs/tools

This command utilizes `dune init lib` to create a new OCaml library named 'my_lib' at the specified path within the current project. It ensures the operation is performed in the correct OCaml environment via `opam exec`. The output confirms successful library initialization.

```Shell
$ opam exec -- dune init lib my_lib ./path/to/my_lib
Success: initialized library component named my_lib
```

--------------------------------

### Create and Navigate to OCaml Project Directory

Source: https://ocaml.org/docs/using-the-ocaml-compiler-toolchain

This command sequence creates a new directory named 'hello' and then changes the current working directory into it, preparing the environment for OCaml project files.

```Shell
mkdir hello
cd hello
```

--------------------------------

### Check Homebrew Installation Path on macOS M1

Source: https://ocaml.org/docs/arm64-fix

Before proceeding with fixes, verify the current Homebrew installation location. This command helps identify if Homebrew is installed in the problematic `/usr/local/bin/brew` path instead of the desired `/opt/homebrew/bin/brew`.

```Shell
where brew
```

--------------------------------

### Dune Executable Configuration (with Library)

Source: https://ocaml.org/docs/libraries-dune

This updated `dune` file for the executable now includes a `(libraries wmo)` stanza. This declares a dependency on the `wmo` library, allowing the `cloud` executable to link against and use modules provided by the library.

```Dune
(executable
  (name cloud)
  (public_name nube)
  (libraries wmo))
```

--------------------------------

### Verify Command Line Tools Installation on macOS

Source: https://ocaml.org/docs/arm64-fix

Ensure the Command Line Tools (CLT) are installed. This command lists the contents of the CLT directory. If they are not installed, they need to be downloaded directly from Apple's Developer website.

```Shell
ls /Library/Developer/CommandLineTools
```

--------------------------------

### Initial OCaml Program with Hardcoded Dependencies

Source: https://ocaml.org/docs/functors

This initial version of the 'funkt.ml' program processes input lines, splits them into words, collects unique words, and then prints them. It implicitly depends on the 'List' and 'Out_channel' modules for its functionality.

```OCaml
module StringSet = Set.Make(String)

module IterPrint : sig
  val f : string list -> unit
end = struct
  let f = List.iter (fun s -> Out_channel.output_string stdout (s ^ "\n"))
end

let _ =
  stdin
  |> In_channel.input_lines
  |> List.concat_map Str.(split (regexp "[ \t.,;:()]+"))
  |> StringSet.of_list
  |> StringSet.elements
  |> IterPrint.f
```

--------------------------------

### Basic OCaml 'Hello, World!' Program

Source: https://ocaml.org/docs/your-first-program

The content of the `bin/main.ml` file, which serves as the primary entry point for the 'hello' application. This simple OCaml code snippet demonstrates how to print a string to the console using `print_endline`.

```OCaml
let () = print_endline "Hello, World!"
```

--------------------------------

### OCaml: Creating a Record Instance

Source: https://ocaml.org/docs/language

This example shows how to create an instance of the previously defined `name` record type. The `robin` record is initialized with specific `first` and `last` names, preparing it for destructuring in a later pattern matching demonstration.

```OCaml
# let robin = { first = "Robin"; last = "Milner" };;
val robin : name = {first = "Robin"; last = "Milner"}
```

--------------------------------

### Project Directory Structure

Source: https://ocaml.org/docs/libraries-dune

This output from the `tree` command shows the resulting file and directory structure of the minimal OCaml project. It illustrates the placement of Dune configuration files and OCaml source files.

```Shell
.
├── dune
├── dune-project
├── cloud.ml
└── wmo.ml
```

--------------------------------

### Create New OCaml Library with Dune

Source: https://ocaml.org/docs/bootstrapping-a-dune-project

This command uses `dune init lib` to create a new OCaml library component named 'my_lib' within the current project. It sets up the necessary directory structure and files for a new library. The path specifies where the library files will be created.

```Shell
$ opam exec -- dune init lib my_lib ./path/to/my_lib
Success: initialized library component named my_lib
```

--------------------------------

### Install Sexplib OCaml Package

Source: https://ocaml.org/docs/your-first-program

This command uses the opam package manager to install the Sexplib library, which is essential for parsing and manipulating S-expressions in OCaml projects.

```Shell
opam install sexplib
```

--------------------------------

### Initialize New OCaml Project Directory

Source: https://ocaml.org/docs/using-the-ocaml-compiler-toolchain

These shell commands create a new directory named `myproject` and then navigate into it. This is the initial step for setting up a new OCaml project, typically followed by creating Dune configuration files.

```Shell
mkdir myproject
cd myproject
```

--------------------------------

### Install Specific OCaml Package Version with opam

Source: https://ocaml.org/docs/managing-dependencies

Use this command to install a particular version of an OCaml package from the opam repository. This is useful for maintaining compatibility or working with older project requirements.

```Shell
opam install <package-name>.<package-version>
```

--------------------------------

### Loading a Pre-Processor Extension (PPX) in OCaml UTop

Source: https://ocaml.org/docs/toplevel-introduction

Illustrates how to activate a Pre-Processor Extension (PPX) in the OCaml UTop environment using the `#require` directive. This command loads the specified PPX library, such as `ppx_deriving.show`, enabling its code generation capabilities. It assumes the corresponding opam package is already installed in the OCaml switch.

```OCaml
#require "ppx_deriving.show"
```

--------------------------------

### Example Usage of Composed Logging Function

Source: https://ocaml.org/docs/monads

Provides a simple example of calling the composed logging function `id'` with an initial value and an empty log string, illustrating its usage and the required input format.

```OCaml
id' (5, "")
```

--------------------------------

### Configure Dune for Source Preprocessing

Source: https://ocaml.org/docs/metaprogramming

This Dune file stanza configures an executable named 'hello' to apply a source preprocessor. It uses the `preprocess` action with a `run` command to execute `preprocessor.sh` on the input file.

```Dune
(executable
 (name hello)
 (preprocess
  (action
   (run ./preprocessor.sh %{input-file}))))
```

--------------------------------

### Install Latest OCaml Package with opam

Source: https://ocaml.org/docs/managing-dependencies

This command installs the latest available version of a specified package from the opam repository into your active OCaml switch. It's the standard way to add new libraries to your project.

```Shell
opam install <package-name>
```

--------------------------------

### OCaml Library Wrapper File for WMO

Source: https://ocaml.org/docs/libraries-dune

This OCaml code defines a manual wrapper file (`wmo.ml`) for a library. It explicitly exposes `Cumulus` and `Stratus` as submodules, allowing fine-grained control over the library's public interface.

```OCaml
module Cumulus = Cumulus
module Stratus = Stratus

```

--------------------------------

### OCaml Monadic Bind Operator Usage Example

Source: https://ocaml.org/docs/monads

A concise example demonstrating the use of the monadic bind operator (`>>=`) in OCaml to sequence operations within a monadic context, where `m` is a monadic value and `f` is a function that processes its result.

```OCaml
m >>= fun x ->
    log name f x
```
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