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OCaml

typed functional programming compilers tools and formal methods

English

Definition first

What OCaml means

OCaml is a programming language for writing exact instructions, often used for typed functional programming compilers tools and formal methods. Start with one mental model: input goes through steps and becomes output.

Minimum run factsFile main.mlRun ocaml main.mlHabit Use pattern matching and keep type signatures readable
Program

An ordered set of instructions. It reads input, follows rules, and produces output.

Value and variable

A value is data. A variable is the name you use to hold and reuse that data.

Function

A named piece of work. It takes input, does one job, and can return a result.

Runtime

OCaml is the place that actually runs code from main.ml.

First readable code

Program output

entry point output syntax print_int
print_int 42
Output 42

Language lineage

OCaml family tree

See where OCaml comes from, which languages feel close, and what to learn next.

roots
MLCamlLambda calculus
currentOCamlML functional family
familyML functional family
best used for

compilers, theorem tools, and precise functional programs

Zero base path

1Read one rule2Predict output3Type from memory4Run checklist5Repeat with one change

Question bank

Search before practice

Pick a stage or search across the open programming bank. Jump straight to the matching drill.

18 matching questions
Q 1ChoiceStage 1 definitions

OCaml practice 1

OCaml question 1. Choose the statement that matches printing a value.

Q 2ChoiceStage 1 definitions

OCaml practice 2

OCaml question 2. Choose the statement that matches naming a value.

Q 3ChoiceStage 1 definitions

OCaml practice 3

OCaml question 3. Choose the statement that matches reusable function.

Q 4ChoiceStage 1 definitions

OCaml practice 4

OCaml question 4. Choose the statement that matches basic collection.

Q 5ChoiceStage 1 definitions

OCaml practice 5

OCaml question 5. Choose the statement that matches printing a value.

Q 6ChoiceStage 1 definitions

OCaml practice 6

OCaml question 6. Choose the statement that matches naming a value.

Q 7ChoiceStage 1 definitions

OCaml practice 7

OCaml question 7. Choose the statement that matches reusable function.

Q 8ChoiceStage 1 definitions

OCaml practice 8

OCaml question 8. Choose the statement that matches basic collection.

Q 9ChoiceStage 1 definitions

OCaml practice 9

OCaml question 9. Choose the statement that matches printing a value.

Q 10ChoiceStage 1 definitions

OCaml practice 10

OCaml question 10. Choose the statement that matches naming a value.

Q 11ChoiceStage 1 definitions

OCaml practice 11

OCaml question 11. Choose the statement that matches reusable function.

Q 12ChoiceStage 1 definitions

OCaml practice 12

OCaml question 12. Choose the statement that matches basic collection.

Q 13ChoiceStage 1 definitions

OCaml practice 13

OCaml question 13. Choose the statement that matches printing a value.

Q 14ChoiceStage 1 definitions

OCaml practice 14

OCaml question 14. Choose the statement that matches naming a value.

Q 15ChoiceStage 1 definitions

OCaml practice 15

OCaml question 15. Choose the statement that matches reusable function.

Q 16ChoiceStage 1 definitions

OCaml practice 16

OCaml question 16. Choose the statement that matches basic collection.

Q 17ChoiceStage 1 definitions

OCaml practice 17

OCaml question 17. Choose the statement that matches printing a value.

Q 18ChoiceStage 1 definitions

OCaml practice 18

OCaml question 18. Choose the statement that matches naming a value.

Multiple choice

OCaml practice 1

Q 1Choicenew

OCaml question 1. Choose the statement that matches printing a value.

print_int 42

Reference

Patterns for main.ml

OCamlocaml main.ml
Recall from memoryRead a small point then write it back without looking
Trace the codeWrite variable values line by line before you run the answer
Type it yourselfCopy less type more and fix one small error at a time

entry point output syntax print_int

Program output

print_int 42
  • Run the smallest file first
  • Print one known value
  • Check the output before adding more code

variables assignment types let

Values and names

let total = 42
let () = print_int total
  • Give values readable names
  • Keep one idea per line while learning
  • Trace the value before changing it

function collection List

Functions and collections

let add a b =
  a + b

let scores = [40; 2]
let () = print_int (List.length scores)
  • Keep functions small
  • Return useful values
  • Use the common collection before reaching for frameworks