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Document CofreeType.zip.

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Rob Rix 2015-10-22 18:09:18 -04:00
parent 7b57a9ce17
commit c84578402c
1 changed files with 3 additions and 0 deletions
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prototype/Doubt/Cofree.swift
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@ -125,6 +125,9 @@ extension CofreeType {
return (Wrap(seed) <<< { $0.map(coiterate(unfold)) } <<< unfold) <| seed
}
/// `Zip` two `CofreeType` values into a single `Cofree`, pairing their annotations.
///
/// This is partial, returning `nil` for any pair of values which are not of the same “shape,” i.e. where they wrap `Syntax` values of different constructors. The values of leaves are always taken from the second parameter.
public static func zip(a: Self, _ b: Self) -> Cofree<Leaf, (Annotation, Annotation)>? {
let annotations = (a.extract, b.extract)
switch (a.unwrap, b.unwrap) {