aivi.core.set

aivi.core.set provides immutable sets for values with an Eq instance. A Set A is list-backed, so membership and updates take linear time and fromList can take quadratic time. Use it for small membership collections in the MVP.

The public representation is { items: List A }, but direct record construction can contain duplicates. singleton, insert, and fromList preserve uniqueness and insertion order.

Type class operations

This module's Set implements Foldable: ambient reduce visits each member once in insertion order. Default (Set A) creates an empty set. These operations need no equality comparisons.

An unrestricted Functor Set would need equality evidence for the mapped element type and could merge distinct members. Use operations that make that change of membership explicit.

API

Export	Type	Behavior
Set	Set A	List-backed set record type
isEmpty	Set A -> Bool	Test whether the set has no items
singleton	A -> Set A	Create a one-item set
member	Eq A => A -> Set A -> Bool	Test membership
insert	Eq A => A -> Set A -> Set A	Add an item if absent
remove	Eq A => A -> Set A -> Set A	Remove an item if present
size	Set A -> Int	Count items
toList	Set A -> List A	Return items in insertion order
fromList	Eq A => List A -> Set A	Build a set and discard duplicates

use aivi.core.set (
    Set
    fromList
    member
)

value tags : Set Text =
    fromList [
        "work",
        "urgent",
        "work"
    ]

value isUrgent : Bool = member "urgent" tags