Coupling analysis for containers (modules/classes).

Measures dependencies between containers. Low coupling is desirable for maintainability.

Coupling Types

• Afferent Coupling (Ca): Number of containers that depend on this container
• Efferent Coupling (Ce): Number of containers this container depends on
• Instability (I): Ce / (Ca + Ce) - ranges from 0 (stable) to 1 (unstable)

Assessment

• Low coupling (Ce < 5): Excellent - easy to test and maintain
• Moderate coupling (5 <= Ce < 10): Good - acceptable dependencies
• High coupling (10 <= Ce < 20): Fair - consider refactoring
• Very high coupling (Ce >= 20): Poor - difficult to maintain

Examples

# Low coupling - no external dependencies
ast = {:container, [container_type: :class, name: "Calculator"], [
  {:function_def, [name: "add", params: ["x", "y"], visibility: :public], [
   {:binary_op, [category: :arithmetic, operator: :+], [{:variable, [], "x"}, {:variable, [], "y"}]}]}
]}

doc = Document.new(ast, :python)
{:ok, result} = Coupling.analyze(doc)
result.efferent_coupling  # => 0
result.assessment         # => :excellent