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|
let less_than_natural: Relation.t =
let rec generator (position: int option): Generator.result =
let pair_of_nat n =
let nf = float_of_int n in
let r =
int_of_float (floor ((1. +. sqrt (1. +. 8. *. nf)) /. 2.))
in
let t_prev = (r * (r - 1)) / 2 in
let left = n - t_prev in
(left, r) in
match position with
| Some position ->
let left, right = pair_of_nat position in
let attributes: Attribute.materialized Tuple.AttributeMap.t =
Tuple.AttributeMap.of_list [("left", Obj.magic left); ("right", Obj.magic right)]
in Generator.Value (Tuple.make_materialized ~relation: "less_than" ~attributes: attributes, generator)
| None -> Error "Cannot produce a randomly enumerated value for less_than over naturals."
in let membership_criteria: Tuple.t -> bool = function
| Tuple.Materialized materialized ->
let left = Tuple.AttributeMap.find "left" materialized.attributes
in let right = Tuple.AttributeMap.find "right" materialized.attributes
in left < right
| Tuple.NonMaterialized _non_materialized -> false (* TODO: Handle references later *)
in Relation.make
~hash: None
~name: "natural_natural_less_than"
~schema: (Schema.empty |> Schema.add "left" "natural" |> Schema.add "right" "natural")
~tree: None
~constraints: None
~cardinality: Conventions.Cardinality.AlephZero
~generator: (Some generator)
~membership_criteria: membership_criteria
~provenance: (Relation.Provenance.Base "less_than")
~lineage: (Relation.Lineage.Base "less_than")
|
