LocalsNone

LocalsNone is a term used in programming and software engineering to denote a sentinel value that signals the absence of a local execution context, typically the absence of local variables within a function or block. It is not a standard keyword in mainstream languages, but appears in discussions, libraries, or tooling that model or inspect symbol tables and scopes. The term blends "locals" and "None" (or null) to convey emptiness.

In practice, localsNone would be used as a placeholder in APIs that pass around a mapping of local bindings or in debug traces to indicate "no locals." For example, an interpreter might return localsNone instead of an empty mapping to save allocations or to distinguish an explicitly empty scope from a scope with no data.

The concept intersects with sentinel values and the practice of using a dedicated constant to avoid null checks. Implementers should document semantics to avoid confusion with a valid empty mapping or with a true None/null value, and ensure comparability and immutability where applicable.

In languages that already have clear representations of absence (such as None in Python, null in Java and C#), localsNone is typically considered a domain-specific abstraction rather than a universal feature. Some tooling prefers using standard empty mappings or optional types instead of a sentinel.

See also: locals(), sentinel value, null, None, symbol table, scope.