std/hashable

Import with import std/hashable.

Exports

Interfaces

• Hashable

interface Hashable

interface Hashable {
    fn hash(value: self): Int
}

Protocol for producing an Int hash that respects structural equality.

Hashable.hash(value) returns an Int such that Equatable.equal?(a, b) implies Hashable.hash(a) == Hashable.hash(b). Used by hash-based collections (Map and friends) to bucket values by structural identity. The hash is not cryptographic and may change between runs of the runtime; it is suitable only for in-process bucketing.

All four primitive types — Int, Float, Bool, String — implement Hashable. To implement it for a custom type:

pub struct Point {
  x: Int
  y: Int
}

impl Hashable for Point {
  fn hash(p: Point): Int { Hashable.hash(p.x) + Hashable.hash(p.y) * 31 }
}

derive Hashable synthesizes a structural hash for structs (mixing all field hashes), enums (mixing the variant tag and payload), and distinct types (delegating to the inner value).