Hashed<T> represents a type T by its hash.
Since a hash is only a single field element, this can be more efficient in provable code where the number of constraints depends on the number of field elements per value.
For example, Provable.if(bool, x, y) takes O(n) constraints, where n is the number of field
elements in x and y. With Hashed, this is reduced to O(1).
The downside is that you will pay the overhead of hashing your values, so it helps to experiment in which parts of your code a hashed representation is beneficial.
Usage:
// define a hashed type from a type
let HashedType = Hashed.create(MyType);
// hash a value
let hashed = HashedType.hash(value);
// ... operations on hashes, more efficient than on plain values ...
// unhash to get the original value
let value = hashed.unhash();Warning: When wrapping a type with Hashed, make sure that that type is safe to automatically pack
and unpack in provable code. In particular, do not use Hashed with types that define a custom toInput()
(specifying a certain bit packing) but no corresponding check() method (that constrains the bit lengths of the packed parts).
• T
new Hashed<T>(hash: Field, value: Unconstrained<T>): Hashed<T>• hash: Field
• value: Unconstrained<T>
Hashed<T>
hash: Field;value: Unconstrained<T>;static _innerProvable: undefined | ProvableHashable<any>;static _provable: undefined | ProvableHashable<Hashed<any>>;get Constructor(): typeof Hashedtypeof Hashed
get static innerProvable(): ProvableHashable<any>ProvableHashable<any>
toFields(): Field[]Field[]
unhash(): TUnwrap a value from its hashed variant.
T
static _hash(_: any): Field• _: any
static create<T>(type: WithProvable<ProvableHashable<T>>, hash?: (t: T) => Field): typeof Hashed & {
"provable": ProvableHashable<Hashed<T>>;
"empty": Hashed<T>;
}Create a hashed representation of type. You can then use HashedType.hash(x) to wrap a value in a Hashed.
• T
• type: WithProvable<ProvableHashable<T>>
• hash?
typeof Hashed & {
"provable": ProvableHashable<Hashed<T>>;
"empty": Hashed<T>;
}
static hash<T>(value: T, hash?: Field): Hashed<T>Wrap a value, and represent it by its hash in provable code.
let hashed = HashedType.hash(value);Optionally, if you already have the hash, you can pass it in and avoid recomputing it.
• T
• value: T
• hash?: Field
Hashed<T>