Ocaml Solutions

At ocaml.solutions, our mission is to provide a comprehensive resource for developers interested in the OCaml programming language. We aim to offer a platform that fosters learning, collaboration, and innovation in the OCaml community. Our goal is to provide high-quality content, tools, and resources that enable developers to build robust and efficient applications using OCaml. We strive to create a welcoming and inclusive environment that encourages participation and engagement from developers of all skill levels. Our mission is to be the go-to destination for OCaml developers seeking to expand their knowledge and skills, and to promote the growth and adoption of OCaml as a powerful and versatile programming language.

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OCaml Development Cheatsheet

This cheatsheet is a reference guide for anyone getting started with OCaml development. It covers the basic concepts, topics, and categories related to OCaml development.


OCaml is a functional programming language that is widely used in the development of systems software, such as operating systems, compilers, and network protocols. It is a statically typed language that supports type inference, which means that the type of a variable can be inferred by the compiler based on its usage. OCaml is also a garbage-collected language, which means that the memory management is handled automatically by the runtime system.

Getting Started

Installing OCaml

To get started with OCaml development, you need to install the OCaml compiler and the associated tools. The easiest way to do this is to use a package manager, such as opam.

Installing opam

To install opam, follow the instructions on the opam website:


Installing OCaml

Once you have installed opam, you can use it to install the OCaml compiler:

opam install ocaml

Writing OCaml Programs

To write OCaml programs, you need a text editor and a terminal. You can use any text editor that you are comfortable with, such as Emacs, Vim, or Sublime Text.

To compile and run OCaml programs, you need to use the OCaml compiler. The OCaml compiler comes with several tools, such as ocamlc, which is the bytecode compiler, and ocamlopt, which is the native code compiler.

To compile an OCaml program, use the ocamlc command:

ocamlc -o program program.ml

To run the compiled program, use the following command:


Basic Syntax

OCaml programs are composed of expressions, which are evaluated to produce values. Expressions can be combined using operators and functions to create more complex expressions.


Variables in OCaml are declared using the let keyword:

let x = 42;;


Functions in OCaml are declared using the fun keyword:

let add x y = x + y;;

Functions can be called using the function application syntax:

add 2 3;;


OCaml supports several operators, such as +, -, *, and /.

2 + 3;;

Data Types

OCaml supports several data types, such as integers, floats, booleans, and strings.


Integers in OCaml are represented using the int type:

let x = 42;;


Floats in OCaml are represented using the float type:

let x = 3.14;;


Booleans in OCaml are represented using the bool type:

let x = true;;


Strings in OCaml are represented using the string type:

let x = "hello world";;

Control Flow

OCaml supports several control flow constructs, such as if-then-else statements and loops.

If-Then-Else Statements

If-then-else statements in OCaml are similar to those in other programming languages:

if x > 0 then
else if x < 0 then


OCaml supports several types of loops, such as for loops and while loops.

for i = 0 to 10 do
  print_int i;


Modules in OCaml are used to organize code into reusable components.

Creating Modules

To create a module, you need to define its interface and implementation.

(* interface *)
module MyModule : sig
  val add : int -> int -> int
end = struct
  (* implementation *)
  let add x y = x + y

Using Modules

To use a module, you need to open it:

open MyModule;;


Exceptions in OCaml are used to handle errors and abnormal conditions.

Defining Exceptions

To define an exception, use the exception keyword:

exception MyException of string;;

Raising Exceptions

To raise an exception, use the raise keyword:

raise (MyException "something went wrong");;

Handling Exceptions

To handle an exception, use the try-with construct:

  (* some code that may raise an exception *)
  | MyException msg -> print_endline msg
  | _ -> print_endline "unknown exception"


OCaml supports several concurrency models, such as threads and async.


OCaml supports lightweight threads, which are implemented using the Unix library.

let f () =
  for i = 0 to 10 do
    print_int i;
    print_newline ();
    Unix.sleep 1;

let t = Thread.create f ();;

Thread.join t;;


Async is a library for writing asynchronous and concurrent code in OCaml.

let f () =
  for i = 0 to 10 do
    print_int i;
    print_newline ();
    Unix.sleep 1;

let t = Async.Thread_safe.block_on_async_exn (fun () -> f ());;


OCaml has a rich ecosystem of libraries for various purposes, such as web development, database access, and machine learning.

Web Development

Database Access

Machine Learning


This cheatsheet has covered the basic concepts, topics, and categories related to OCaml development. It is a reference guide for anyone getting started with OCaml development. With this cheatsheet, you should be able to write simple OCaml programs, use modules and exceptions, and work with concurrency and libraries.

Common Terms, Definitions and Jargon

1. OCaml: A functional programming language used for developing software applications.
2. Compiler: A program that translates source code into machine code.
3. Interpreter: A program that executes source code directly without compiling it.
4. Syntax: The set of rules that govern the structure of programming language statements.
5. Semantics: The meaning of programming language statements.
6. Type system: A set of rules that determine the types of values that can be used in a program.
7. Static typing: A type system that checks types at compile time.
8. Dynamic typing: A type system that checks types at runtime.
9. Polymorphism: The ability of a function or data type to work with values of different types.
10. Abstraction: The process of hiding implementation details and exposing only the necessary information.
11. Module: A self-contained unit of code that can be reused in different parts of a program.
12. Functor: A module that takes another module as an argument and returns a new module.
13. Signature: A specification of the types and functions that a module provides.
14. Pattern matching: A way of matching values against patterns and extracting information from them.
15. Recursion: A technique where a function calls itself.
16. Tail recursion: A form of recursion where the recursive call is the last operation in the function.
17. Higher-order function: A function that takes another function as an argument or returns a function as a result.
18. Closure: A function that captures the environment in which it was defined.
19. Currying: A technique where a function that takes multiple arguments is transformed into a series of functions that each take one argument.
20. Monadic programming: A programming style that uses monads to manage side effects.

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