Keyword false

Definition

false is a boolean literal keyword used to express a truth value directly in code.

The keyword false expresses a boolean truth directly. It matters because it avoids implicit conventions and keeps the decision visible in the source code.

Grammatical role

Provides the boolean false value.

This grammatical role is essential: if a reader understands the structural place of false, they already understand much of the diagnostics that will appear when it is moved or truncated.

Canonical syntax

Canonical form: `give false`.

The canonical form matters because it gives the compiler and the reader the same reference structure. A large share of diagnostics related to false come from an abbreviated, displaced, or incomplete form.

Detailed semantics

Semantically, false carries an immediate and unambiguous meaning. It introduces no extra computation; it directly fixes the logical state expected by the branch, guard, or return value.

In an encyclopedic reading, false should not be reduced to a dictionary definition. Its effect on scope, block shape, value visibility, control progression, and the diagnostic family it activates when misused must also be considered.

Effect on execution

false injects a truth value directly into execution and simplifies the reading of guards and returns.

In other words, the presence of false is not merely syntactic: it helps the reader predict what will be executed, produced, exposed, or forbidden from this point in the program.

Valid variants

• `give false`.

These variants are not free synonyms. They indicate the legitimate forms from which one can reason about diagnostics, scope differences, or contract readability.

Vitte example

proc flag() -> bool {
  give false
}

This example shows false in a nominal context. It should be read globally: where the contract begins, which values are constrained, which output becomes observable, and why the presence of the keyword is justified.

Guided reading of the example

1. First locate the full construction that contains false, not the isolated word.
2. Then identify which contract becomes visible because of false: type, branch, binding, module, exit, or advanced boundary.
3. Finish by checking the observable effect produced by the construction that contains false.

This guided reading is intentionally closer to a reference page than to a tutorial: it helps reconstruct the exact role of false in a complete block.

Comparison with C

int flag(void) {
  return 0;
}

This C comparison is structural: it aligns the role of the keyword with a familiar surface without claiming that the two languages carry exactly the same contracts.

The source of truth remains Vitte grammar and semantics. The comparison with C should be read as a cultural marker, not as a parallel specification.

Recommended uses

false deserves to appear when it simplifies the reading of the block's global contract, not when it merely adds one more surface form.

When to use it

• When false makes the block contract more explicit at first reading.
• When it reduces the number of implicit assumptions the reader must reconstruct mentally.
• When a branch, guard, or return must carry a boolean truth without hidden convention.

When to avoid it

• Avoid false when another, more precise keyword already carries the block's intent.
• Avoid false when it adds only surface noise without clarifying the contract.
• Avoid reading or teaching it as an isolated token with no relation to the full structure.

Common pitfalls

• Using false in a grammatical layer where it does not belong.
• Confusing the role of the keyword with the role of the full surrounding block.
• Showing only the nominal form and never how the contract fails.

Invalid example and diagnostic

proc bad_flag() -> bool {
  give 1
}

The literal is used to express a boolean result; the invalid variant mixes the wrong surface.

The counter-example is not merely wrong: it is wrong in an instructive way. It shows which grammar or execution-contract assumption is no longer accepted when false is moved, truncated, or combined with the wrong context. Concretely, the literal value used is not coherent with the expected boolean contract.

A good encyclopedic counter-example does not show arbitrarily broken code: it isolates the precise reason why false can no longer support the expected contract. Its teaching value is diagnostic before it is syntactic.

Common compilation errors

This table does not replace the compiler's exact diagnostics. It serves as a mental map: when false fails, the problem usually comes from an invalid grammatical form, an incoherent type contract, or an incomplete construction.

Neighbor keywords

Comparison with neighboring keywords is essential on a wiki-style page: false is better understood when one knows precisely what it does not do.

Common misreadings

• Reducing false to a local token instead of reading it as part of a full construction.
• Explaining only the syntax and forgetting the reading or diagnostic contract it imposes.

Implementation and diagnostic notes

• A useful diagnostic for this keyword should always connect the observed syntax to the expected contract.
• From the compiler's point of view, this keyword should remain identifiable early enough to produce coherent, localized messages.

Presence in the book

• docs/book/chapters/05-types.html
• docs/book/chapters/07-control.html
• docs/book/chapters/27-grammar.html

See also

• docs/book/chapters/keywords/erreurs-compilateur.html
• docs/book/chapters/keywords/true.html
• docs/book/glossary.html