Vitte

2. Variables and Types

Level: beginner · Reading time: 3 min · Prerequisite: book/poche/01-first-program.html · Last review: 2026-05-09

TL;DR (5 lines)

  • Read the core idea first.
  • Understand one concept at a time.
  • Run small examples.
  • Fix errors early.
  • Move to next chapter only when clear.

Frequent mistakes

  • Skipping prerequisites.
  • Reading without trying examples.
  • Fixing too many errors at once.

Prerequisites: book/poche/01-first-program.html. See also: book/chapters/05-types.html.

Goal

Declare a variable and understand its type.

Example

entry main at app/demo {
  let age: int = 42
  return age
}

Why it matters

An explicit type avoids a lot of invisible errors.

Quick check

If age becomes string, what should be changed?

Try this

  1. Create 2 variables (int, string).
  2. Return a simple value.
  3. Check for possible errors.

If you're stuck

Keep let nom: type = valeur everywhere at the start of learning.

See also

Next best action

Apply one idea from this chapter in a tiny example, then continue.