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  1. Fix Homebrew Errors on Apple M1

    Install CLT

    If they're not installed, let's install them now. You don't have to install all of XCode; you can install just the CLT by downloading them directly from Apple's Developer . Look for a non-beta versi

    Resources

  2. Profiling

    Further Reading

    <!--### Java dynamic dispatch **There are some serious mistakes in the last paragraph:** * Dynamic method dispatch itself is seldom a performance problem. In languages without multiple inheritance

    Guides

  3. Values and Functions

    Introduction

    We use UTop to understand these concepts by example. You are encouraged to modify the examples to gain a better understanding. In OCaml, functions are treated as values, so you can use functions as

    Introduction

  4. Maps

    Changing the Value Associated With a Key

    You should experiment with different update functions; several behaviors are possible. To change a key's associated value, use the update function. It takes a key, a map, and an update functio

    Data Structures

  5. OCaml Programming Guidelines

    Iterators

    In case of express need, be sure to add an explanatory comment. In my opinion, it's absolutely necessary! <!-- $MDX skip --> even though you get: <!-- $MDX skip --> On the other hand, avoid w

    Resources

  6. OCaml Programming Guidelines

    How to Compile

    The make utility is indispensable for managing the compilation and recompilation of programs. Sample make files can be found on The Hump . You can also consult the Makefiles for the OCam

    Resources

  7. Memory Representation of Values

    Conclusion

    Understanding the Garbage Collector Calling C Libraries Other recommended tutorials: We covered the precise mapping from OCaml types to their internal runtime representation in memory, which shou

    Runtime & Compiler

  8. Profiling

    Tail Recursion

    So that's pretty conclusive. Calling Tail__loop_56 will first print the string, and then jump back to the top, then print the string, and jump back, and so on forever. It's a simple loop, not

    Guides

  9. Values and Functions

    Pattern Matching on User-Defined Types

    This also works with user-defined types.

    Introduction

  10. Values and Functions

    Closures

    Inside the max_42 function, the environment contains an additional binding between the first parameter of max and the value 42. Partially applying arguments to a function also creates a new clo

    Introduction

  11. Basic Data Types and Pattern Matching

    Characters

    The module Uchar provides support for Unicode characters. Operations on char values are provided by the Stdlib and the Char modules. Values of type char correspond to the 256 symbols of

    Introduction

  12. Error Handling

    Language Bugs

    Here is an example of such a bug: <https://github.com/ocaml/ocaml/issues/7241> Make sure the crash affects both compilers: bytecode and native Write a self-contained and minimal proof-of-concept co

    Guides

  13. Objects

    A Note About self

    The reference to self names the object, allowing you to call methods in the same class or pass the object to functions outside the class. In other words, it's exactly the same as this in C++

    Advanced Topics

  14. Arrays

    Folding an Array

    These functions derive a single value from the whole array. For example, they can be used to find the maximum element of an array: fold_right f a init computes f a.(0) (f a.(1) ( ... (f a.(n-1)

    Data Structures

  15. Maps

    Maps With Custom Key Types

    Note that our module has a type t and also a compare function. Now we can call the Map.Make functor to get a map for non-negative numbers: We'll start by defining a module for strings th

    Data Structures

  16. A Tour of OCaml

    Functions

    Some functions, such as String.ends_with have labelled parameters. Labels are useful when a function has several parameters of the same type; naming arguments allows to guess their purpose. Above,

    First Steps

  17. OCaml Programming Guidelines

    Naming Complex Arguments

    <!-- $MDX skip --> write <!-- $MDX skip --> In place of

    Resources

  18. Modules

    Submodule Implementation

    dune Definitions from a submodule are accessed by chaining module names, here Florence.Hello.print . Here is the updated dune file, with an additional executable: glasgow.ml florence.ml

    Module System

  19. Loops and Recursions

    Recursion

    In the first example, we'll read the whole file into memory (into a long string). There are essentially three possible approaches to this: Writing recursive functions requires a change in mindse

    Introduction

  20. Maps

    Finding Entries in a Map

    Note that find_first_opt and find_last_opt return the key-value pair, not just the value. The functions find_first and find_last behave similarly, except they throw exceptions instead of

    Data Structures

  21. Options

    The Standard Library Option Module

    Most of the functions in this section, as well as other useful ones, are provided by the OCaml standard library in the Stdlib.Option module.

    Data Structures

  22. Error Handling

    Exceptions

    Here, we add a variant Foo to the type exn and create a function that will raise this exception. Now, how do we handle exceptions? The construct is try ... with ... : Exceptions belong to

    Guides

  23. Basic Data Types and Pattern Matching

    Results

    Operations on results are provided by the Result module. Results are discussed in the Error Handling guide. The result type can be used to express that a function's outcome can be either succ

    Introduction

  24. File Manipulation

    Gotchas

    Don't forget to flush your out_channel s if you want to actually write something. This is particularly important if you are writing to non-files such as the standard output ( stdout ) or a socke

    Tutorials

  25. OCaml on Windows

    Vim and Emacs

    If you use Vim , the default Cygwin Vim will not work with Merlin. You will need install Vim separately. In addition to the usual instructions printed when installing Merlin, you may need to se

    Resources

  26. Mutability and Imperative Control Flow

    Arrays

    For a more detailed discussion on arrays, see the Arrays tutorial. the array location to update (when on the left-hand side of <- ), or the cell's content (when on the right-hand side of <- ). T

    Introduction

  27. File Manipulation

    Buffered Channels

    channels that write to a file: type out_channel channels that read from a file: type in_channel The normal way of opening a file in OCaml returns a channel . There are two kinds of channels:

    Tutorials

  28. Arrays

    Modifying Array Elements

    Note that this operation returns unit , not the modified array. even_numbers is modified in place as a side effect. To modify an element in an array, we simply assign a new value to it using th

    Data Structures

  29. Debugging

    Setting Break Points

    Now we can guess why List.assoc will fail to find "INRIA" in the list... Then, we can step and find what happens just before ( <|b|> ) List.assoc is about to be called in find_address : L

    Guides

  30. Configuring Your Editor

    Windows Users

    If you used the DkML distribution, you will need to: 1. Go to File > Preferences > Settings view (or press Ctrl , ) 2. Select User > Extensions > OCaml Platform 3. Uncheck OCaml: U

    Tooling

  31. Your First OCaml Program

    Conclusion

    <!-- TODO: link Project Quickstart If you're already familiar with lists, maps, and folds, and need to be productive as fast as possible, dive into the “Project Quickstart” guide. --> This tuto

    First Steps

  32. Modules

    Submodule With Signatures

    The first version made Florence.Hello.message public. In this version it can't be accessed from glasgow.ml . To define a submodule's interface, we can provide a module signature . This is do

    Module System

  33. Options

    Peel-Off Doubly Wrapped Options

    In the standard library, this is Option.join . Here is join of type 'a option option -> 'a option . It peels off one layer from a doubly wrapped option:

    Data Structures

  34. Arrays

    Accessing Array Elements

    You can access individual elements of an array using the .(index) syntax, with the index of the element you want to access. The index of the first element is 0, and the index of the last element

    Data Structures

  35. Basic Data Types and Pattern Matching

    Options

    Operations on options are provided by the Option module. Options are discussed in the Error Handling guide. Here is an example of pattern matching on an option value: The option type is a

    Introduction

  36. Values and Functions

    The Pipe Operator

    This is just like a Unix shell pipe. The pipe operator ( |> ) also avoids parentheses but in reversed order: function on right, argument on left.

    Introduction

  37. OCaml Programming Guidelines

    Delimiters

    A space should always follow a delimiter symbol, and spaces should surround operator symbols. It has been a great step forward in typography to separate words by spaces in order to make written t

    Resources

  38. A Tour of OCaml

    Anonymous Functions

    We can write anonymous functions and immediately apply them to a value: Anonymous functions do not have a name, and they are defined with the fun keyword:

    First Steps

  39. Basic Data Types and Pattern Matching

    Type Aliases

    This is mostly useful as a means of documentation or to shorten long type expressions. Just like values, any type can be given a name.

    Introduction

  40. Installing OCaml

    Join the Community

    Make sure you join the OCaml community . You'll find many community members on Discuss or Discord . These are great places to ask for help if you have any issues.

    First Steps

  41. Operators

    Unary Operators

    This allows users to write more compact code. However, be careful not to write excessively terse code, as it is harder to maintain. Understanding operators must be obvious to most readers, otherwise

    Advanced Topics

  42. Lists

    Association Lists

    When using association lists, and for other purposes, it is sometimes useful to be able to make a list of pairs from a pair of lists and vice versa. The List module provides the functions sp

    Introduction

  43. The Compiler Backend: Bytecode and Native code

    Perf

    <div class="note"> Perf has a growing collection of other commands that let you archive these runs and compare them against each other. You can read more on the home page . This trace broadly

    Runtime & Compiler

  44. Arrays

    Creating Arrays

    Array.init generates an array of a given length by applying a function to each index of the array, starting at 0. The following line of code creates an array containing the first 5 even numbers us

    Data Structures

  45. Your First OCaml Program

    Watch Mode

    Before we dive in, note that you will typically want to use Dune's watch mode to continually compile and optionally restart your program. This ensures that the language server has the freshest poss

    First Steps

  46. Error Handling

    Inherently Unsafe Functions

    Some OCaml functions are inherently unsafe. Use them with care, not like this:

    Guides

  47. Debugging

    The OCaml Debugger

    ocamldebug runs on ocamlc bytecode programs (it does not work on native code executables), and it does not work under native Windows ports of OCaml (but it runs under the Cygwin port). We now

    Guides

  48. Higher Order Functions

    Iterating

    Iterating in OCaml means that if there is one value (or more), we'd like to apply a function to it. But in OCaml the pattern for iteration can be extended to other kinds of data types, like optional

    Introduction

  49. The Compiler Backend: Bytecode and Native code

    Gprof

    Getting precise information out of gprof requires passing the -p flag to the native code compiler when compiling and linking the binary. This generates extra code that records profile infor

    Runtime & Compiler

  50. Lists

    Functions on Lists

    Notice that the memory for the second list is shared, but the first list is effectively copied. Why is this? Because in the pattern _ :: t the head of the list is not inspected, so its type

    Introduction
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