singleton \(\mathrm{singleton}\) — Singleton Class Predicate (singleton, AST Constructor: TpSingleton)
Unary predicate X is a singleton ⟷ ∃(a:Class)(X = {a}) (Entry DefIsSingleton (3.27)).
| Field | Mathematical & Kernel Specification (MKTD1 / MKTD2) |
|---|---|
| Symbol |
singleton
\(\mathrm{singleton}\)
|
| Category | Predicate Symbol (Unary Class Predicate) |
| SML AST Constructor | HP (TpSingleton of 'Class_EXP) [in datatype Truth_p, typetheory.ML:672] |
| Constructor Arguments | 1. Class term X : Class |
| Metatype / Signature | Class → Bool |
| Binder Status | No — Unary Predicate Symbol (Singleton Property) |
| Defining Kernel Entries (ML Labels) | See Related Symbols & Kernel Entries below. |
| LaTeX Form | \mathrm{singleton} |
| How to Understand It | SML AST Constructor: |
| Canonical Law / Usage | (X is a singleton) ⟷ ∃(a:Class)(X = {a}) |
| Related Symbols & Kernel Entries |