∅ / 0 \(\emptyset\) — Empty Set / Zero Ordinal Constant (∅, AST Constructor: CpEmptySet)
0-ary class constant ∅ = {x | ⊥} denoting the unique empty class/set (Entry DefEmptySet (3.04)) and the ordinal 0.
| Field | Mathematical & Kernel Specification (MKTD1 / MKTD2) |
|---|---|
| Symbol |
∅ / 0
\(\emptyset\)
|
| Category | Functional Symbol (0-ary Class Constant) |
| SML AST Constructor | HC CpEmptySet [in datatype Class_p, typetheory.ML:555] |
| Constructor Arguments | 0-ary constant (no arguments) |
| Metatype / Signature | Class |
| Binder Status | No — Defined 0-ary Functional Symbol (Empty Set Constant) |
| Defining Kernel Entries (ML Labels) | See Related Symbols & Kernel Entries below. |
| LaTeX Form | \emptyset |
| How to Understand It | SML AST Constructor: |
| Canonical Law / Usage | ∅ = {x | ⊥} |
| Related Symbols & Kernel Entries |