Learn Ocaml - 10 Code Examples & CST Typing Practice Test

OCaml is a functional, imperative, and object-oriented programming language in the ML family. It features strong static typing, type inference, and a powerful module system, making it suitable for compiler construction, systems programming, and formal verification.

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OCaml Counter and Theme Toggle OCaml Simple Addition OCaml Factorial OCaml Fibonacci Sequence OCaml Max of Two Numbers OCaml List Sum OCaml Even Numbers Filter OCaml Conditional Counter Increment OCaml Resettable Counter OCaml Theme Toggle Only

Learn OCAML with Real Code Examples

Updated Nov 20, 2025

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Code Sample Descriptions

OCaml Counter and Theme Toggle

let count = ref 0
let isDark = ref false

let updateUI () =
  Printf.printf "Counter: %d\n" !count;
  Printf.printf "Theme: %s\n" (if !isDark then "Dark" else "Light")

let increment () = count := !count + 1; updateUI ()
let decrement () = count := !count - 1; updateUI ()
let reset () = count := 0; updateUI ()
let toggleTheme () = isDark := not !isDark; updateUI ()

(* Simulate actions *)
updateUI (); increment (); increment (); toggleTheme (); decrement (); reset ();

Demonstrates a simple counter with theme toggling using OCaml references and functions.

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OCaml Simple Addition

let add a b = a + b
let () = Printf.printf "%d\n" (add 10 20)

Adds two numbers and prints the result.

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OCaml Factorial

let rec factorial n = if n <= 1 then 1 else n * factorial (n - 1)
let () = Printf.printf "%d\n" (factorial 5)

Calculates factorial recursively.

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OCaml Fibonacci Sequence

let rec fib n = if n < 2 then n else fib (n - 1) + fib (n - 2)
let () = for i = 0 to 9 do Printf.printf "%d\n" (fib i) done

Generates first 10 Fibonacci numbers recursively.

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OCaml Max of Two Numbers

let max a b = if a > b then a else b
let () = Printf.printf "%d\n" (max 10 20)

Finds the maximum of two numbers.

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OCaml List Sum

let rec sum_list lst = match lst with [] -> 0 | x::xs -> x + sum_list xs
let () = Printf.printf "%d\n" (sum_list [1;2;3;4;5])

Sums elements of a list recursively.

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OCaml Even Numbers Filter

let print_even lst = List.iter (fun x -> if x mod 2 = 0 then Printf.printf "%d\n" x) lst
let () = print_even [1;2;3;4;5]

Prints even numbers from a list.

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OCaml Conditional Counter Increment

let count = ref 3
if !count < 5 then count := !count + 1
let () = Printf.printf "%d\n" !count

Increment counter only if less than 5.

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OCaml Resettable Counter

let count = ref 0
count := !count + 1
count := !count + 1
let () = Printf.printf "%d\n" !count
count := 0
let () = Printf.printf "%d\n" !count

Counter that increments and can be reset.

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OCaml Theme Toggle Only

let isDark = ref false
let () = Printf.printf "%s\n" (if !isDark then "Dark" else "Light")
isDark := not !isDark
let () = Printf.printf "%s\n" (if !isDark then "Dark" else "Light")
isDark := not !isDark
let () = Printf.printf "%s\n" (if !isDark then "Dark" else "Light")

Toggles theme multiple times.

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Frequently Asked Questions about Ocaml

What is Ocaml?

What are the primary use cases for Ocaml?

Compiler and interpreter development. Formal verification and theorem proving. High-performance and reliable software. Financial modeling and risk analysis. Systems and network programming

What are the strengths of Ocaml?

High reliability due to static typing. Concise and expressive syntax. Efficient native code compilation. Excellent for formal reasoning and verification. Functional and imperative paradigms combined

What are the limitations of Ocaml?

Smaller community than mainstream languages. Fewer third-party libraries and frameworks. Not ideal for GUI-heavy applications. Steep learning curve for beginners. Interop with other ecosystems can be verbose

How can I practice Ocaml typing speed?

CodeSpeedTest offers 10+ real Ocaml code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

OCaml Counter and Theme Toggle

let count = ref 0
let isDark = ref false

let updateUI () =
  Printf.printf "Counter: %d\n" !count;
  Printf.printf "Theme: %s\n" (if !isDark then "Dark" else "Light")

let increment () = count := !count + 1; updateUI ()
let decrement () = count := !count - 1; updateUI ()
let reset () = count := 0; updateUI ()
let toggleTheme () = isDark := not !isDark; updateUI ()

(* Simulate actions *)
updateUI (); increment (); increment (); toggleTheme (); decrement (); reset ();

Demonstrates a simple counter with theme toggling using OCaml references and functions.

Let’s Try →

OCaml Simple Addition

let add a b = a + b
let () = Printf.printf "%d\n" (add 10 20)

Adds two numbers and prints the result.

Let’s Try →

OCaml Factorial

let rec factorial n = if n <= 1 then 1 else n * factorial (n - 1)
let () = Printf.printf "%d\n" (factorial 5)

Calculates factorial recursively.

Let’s Try →

OCaml Fibonacci Sequence

let rec fib n = if n < 2 then n else fib (n - 1) + fib (n - 2)
let () = for i = 0 to 9 do Printf.printf "%d\n" (fib i) done

Generates first 10 Fibonacci numbers recursively.

Let’s Try →

OCaml Max of Two Numbers

let max a b = if a > b then a else b
let () = Printf.printf "%d\n" (max 10 20)

Finds the maximum of two numbers.

Let’s Try →

OCaml List Sum

let rec sum_list lst = match lst with [] -> 0 | x::xs -> x + sum_list xs
let () = Printf.printf "%d\n" (sum_list [1;2;3;4;5])

Sums elements of a list recursively.

Let’s Try →

OCaml Even Numbers Filter

let print_even lst = List.iter (fun x -> if x mod 2 = 0 then Printf.printf "%d\n" x) lst
let () = print_even [1;2;3;4;5]

Prints even numbers from a list.

Let’s Try →

OCaml Conditional Counter Increment

let count = ref 3
if !count < 5 then count := !count + 1
let () = Printf.printf "%d\n" !count

Increment counter only if less than 5.

Let’s Try →

OCaml Resettable Counter

let count = ref 0
count := !count + 1
count := !count + 1
let () = Printf.printf "%d\n" !count
count := 0
let () = Printf.printf "%d\n" !count

Counter that increments and can be reset.

Let’s Try →

OCaml Theme Toggle Only

let isDark = ref false
let () = Printf.printf "%s\n" (if !isDark then "Dark" else "Light")
isDark := not !isDark
let () = Printf.printf "%s\n" (if !isDark then "Dark" else "Light")
isDark := not !isDark
let () = Printf.printf "%s\n" (if !isDark then "Dark" else "Light")

Toggles theme multiple times.

Let’s Try →

Frequently Asked Questions about Ocaml

What is Ocaml?

What are the primary use cases for Ocaml?

Compiler and interpreter development. Formal verification and theorem proving. High-performance and reliable software. Financial modeling and risk analysis. Systems and network programming

What are the strengths of Ocaml?

High reliability due to static typing. Concise and expressive syntax. Efficient native code compilation. Excellent for formal reasoning and verification. Functional and imperative paradigms combined

What are the limitations of Ocaml?

How can I practice Ocaml typing speed?

CodeSpeedTest offers 10+ real Ocaml code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.