fabric.queries
Fabric existence query.
Module nu.context.fabric.queries.
Fabric existence query.
The dual-role read of a FabricRef yields the bound fabric or EMPTY.
That aliases a bound EMPTY, so existence needs an explicit query.
FabricExists holds a FabricRef in a read slot and answers
whether its fabric type is bound on the Context.
| Name | Sort | Call | Meaning |
|---|---|---|---|
| FabricExists | scalar_query | FabricExists(ref) | Whether the fabric type of its FabricRef is bound on the Context. |
FabricExists
Whether the fabric type of its FabricRef is bound on the Context.
FabricExists(ref)Path nu.context.FabricExists. Kind ScalarQuery, sort scalar_query, cardinality scalar. Arity 1 (1 required).
Arguments
| Name | Type | Default | Meaning |
|---|---|---|---|
ref | the FabricRef whose address is resolved and looked up. |
Yields
True or False, never a sentinel.
Notes
- Normally written as
FabricRef(...).exists()rather than built by hand. - Exists because the dual-role read cannot answer the question: an unbound type yields EMPTY, and so does a type bound to EMPTY.
- Answering goes through Context resolution, so a lazily bound factory is materialized by the check itself.
Example
class Counter:
pass
nu.run(nu.FabricRef(Counter).exists())[0]False