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Update HOWITWORKS.md for extensible record matching

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Tony Garnock-Jones 2024-04-04 16:03:00 +02:00
parent 6d1278fbb0
commit ba2bd81f3d
1 changed files with 4 additions and 5 deletions
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syndicate/HOWITWORKS.md
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@ -187,7 +187,7 @@ functions and caches of currently-asserted values.
Index = Bag(V) × Node
Node = Continuation × (Selector ⟼ Class ⟼ Node)
Selector = 𝐍 × 𝐍 -- pop-count and index
Class = X × 𝐍 -- label and arity
Class = X -- label
Continuation = 𝒫(V) × ([H] ⟼ [V] ⟼ Leaf)
Leaf = 𝒫(V) × ([H] ⟼ Handler)
@ -253,12 +253,11 @@ cases where handlers are dynamically installed.
projectMany v [h_0, ...] = [project v h_0, ...]
**Definition.** The `classof` function extracts the constructor label
`x` and its arity `i` from a value `v`, yielding `()` if `v` is not
a record.
`x` from a value `v`, yielding `()` if `v` is not a record.
classof :: V -> 1 + Class
classof a = ()
classof x(v_0, ..., v_i) = (x,i)
classof x(v_0, ..., v_i) = x
**Definition.** The `extend` procedure augments an index with shape
information `s`, by imperatively updating the index structure. It
@ -286,7 +285,7 @@ cases where handlers are dynamically installed.
walk-node h node n_pop n_index x(s_0, ... s_i) =
let (cont, edges) = node
let selector = (n_pop,n_index)
let class = (x,i)
let class = x
if selector not in edges then
edges[selector] := {}
let table = edges[selector]