Status: OUT
Singleton provides controlled sharing infrastructure across all three GoF pattern categories: behaviorally, State subclasses share as Singletons to avoid redundant state objects; structurally, Facade uses Singleton for unified subsystem access points; creationally, Singleton registries enable runtime subclass selection for Abstract Factory and Prototype Manager patterns — making Singleton the catalog's primary sharing-enablement mechanism.
Singleton's lazy initialization and registry mechanisms serve sharing needs across all three GoF categories
Depends on (SL): gof-state-subclasses-often-singletons, facade-often-singleton, singleton-registry-for-subclass-selection