Keyword share

Definition

share is a module-surface keyword used to organize visibility, imports, or sharing.

The keyword share organizes symbol circulation across modules. It clarifies what is imported, shared, renamed, or attached to a visibility boundary.

Grammatical role

Deliberately exposes part of the current module to the outside.

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

Canonical syntax

Canonical form: `share declaration`.

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

Detailed semantics

Semantically, share modifies symbol visibility. It influences how a reader reconstructs the origin of names and how the compiler resolves references.

In an encyclopedic reading, share 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

share acts mainly on name resolution and cross-module visibility. Its execution-time effect is indirect but decisive for the structure of the compiled code.

In other words, the presence of share 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

• `share declaration`
• `share all`

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

space app/core
share proc ping() -> int {
  give 0
}

This example shows share 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 share, not the isolated word.
2. Then identify which contract becomes visible because of share: type, branch, binding, module, exit, or advanced boundary.
3. Finish by checking the observable effect produced by the construction that contains share.
4. For a module keyword, verify the origin and destination of visible symbols.

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

Comparison with C

/* C comparison: imports are usually done with includes and naming conventions instead of module aliases. */

For this keyword, the parallel with C remains approximate. The comparison mainly indicates that in C the same idea is often spread across file conventions, operators, or less explicit control structures.

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

share 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 share makes the block contract more explicit at first reading.
• When it reduces the number of implicit assumptions the reader must reconstruct mentally.
• When the origin or outward exposure of a symbol must stay visible at module level.

When to avoid it

• Avoid share when another, more precise keyword already carries the block's intent.
• Avoid share 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 share 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_share() -> int {
  share
  give 0
}

The module-level surface is misplaced or incomplete.

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 share is moved, truncated, or combined with the wrong context. Concretely, the exported surface is not expressed in a complete form.

A good encyclopedic counter-example does not show arbitrarily broken code: it isolates the precise reason why share 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 share 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: share is better understood when one knows precisely what it does not do.

Common misreadings

• Thinking that share is just syntactic sugar, when it modifies the module's public contract.

Implementation and diagnostic notes

• Common errors concern name resolution, alias collisions, or a shared surface that is too broad or incomplete.
• In a compiler, these keywords participate in cross-file resolution and visible API construction.

Presence in the book

• docs/book/chapters/09-modules.html
• docs/book/chapters/17-stdlib.html
• docs/book/chapters/27-grammar.html

See also

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