04-syntax

Level: beginner · Reading time: 3 min · Prerequisite: book/chapters/03-projet.html · Track: essential · Maturity: reviewed · Last review: 2026-05-09

Prerequisites: book/chapters/03-projet.html. See also: book/chapters/03-projet.html, book/chapters/27-grammar.html, book/chapters/31-build-errors.html.

Concrete Problem

Syntax pages become noisy when they enumerate tokens without showing how a complete block is supposed to look.

Red Thread (Single Project)

One small block shows declarations, expressions, and returns in a single readable flow.

For what

This chapter helps the reader recognize valid Vitte shapes quickly.

What you are going to do

You will read one valid block, map its parts to grammar roles, then inspect an invalid variant that breaks the shape.

Coherent example

space demo/syntax

proc compute(x: int, y: int) -> int {
  let sum: int = x + y
  if sum < 0 { give 0 }
  give sum
}

entry main at core/app {
  return compute(1, 2)
}

Global explanation

Essential syntax is best taught as structure. The reader should see where declarations live, where statements live, and how a block closes with an explicit result.

Invalid case

proc broken(x: int) -> int
  give x
}

This invalid case is intentionally small. It exists to isolate the contract failure that the chapter is trying to teach.

Common pitfalls

• Teaching surface tokens without explaining block shape.
• Using syntax pages to comment every line instead of naming the pattern.
• Confusing grammar shape with later semantic checks.

Short exercise

Add one extra branch and one extra local binding while preserving the same readable block structure.

Summary in 5 points

1. Syntax is about shape before detail.
2. A valid block is the smallest useful teaching unit.
3. Statements and declarations belong to different layers.
4. Invalid examples should isolate shape errors.
5. The reader should leave able to recognize a healthy block instantly.