Evaluation Automaton — Pattern Matching

Documentation status: architecture — see Maturity and evidence.

Pattern matching is a central expression-engine mechanism: it compares a value or structure with a pattern and can enrich the environment with new bindings.

The current engine provides a specialized protocol that associates evaluation functions with explicit matching states.

Conceptual model

value + pattern
  -> compare structure
  -> validate pattern constraints
  -> create compatible bindings
  -> success with enriched environment
     OR explicit failure

Pattern categories

Depending on the expression family, a pattern can represent:

• an atomic value;
• a composite structure;
• a pattern variable;
• a wildcard;
• nested patterns.

Exact language syntax must be documented by the relevant language reference rather than inferred from matcher internals.

Why a specialized automaton?

Matching is more than a Boolean comparison. It may:

• produce bindings;
• fail without producing a business value;
• recurse into structures;
• return to a parent state;
• participate in logical or functional strategies.

It is therefore a natural bridge between functional evaluation and structural reasoning.