Hashed
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).
Type parameters
• T
Constructors
new Hashed()
new Hashed<T>(hash: Field, value: Unconstrained<T>): Hashed<T>
Parameters
• hash: Field
• value: Unconstrained\<T>
Returns
Hashed\<T>
Source
Properties
hash
hash: Field;
Source
value
value: Unconstrained<T>;
Source
_innerProvable
static _innerProvable: undefined | ProvableHashable<any>;
Source
_provable
static _provable: undefined | ProvableHashable<Hashed<any>>;
Source
Accessors
Constructor
get Constructor(): typeof Hashed
Returns
typeof Hashed
Source
innerProvable
get static innerProvable(): ProvableHashable<any>
Returns
ProvableHashable\<any>
Source
Methods
toFields()
toFields(): Field[]
Returns
Field[]
Source
unhash()
unhash(): T
Unwrap a value from its hashed variant.
Returns
T
Source
_hash()
static _hash(_: any): Field
Parameters
• _: any
Returns
Source
create()
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.
Type parameters
• T
Parameters
• type: WithProvable\<ProvableHashable\<T>>
• hash?
Returns
typeof Hashed & {
"provable": ProvableHashable\<Hashed\<T>>;
"empty": Hashed\<T>;
}
Source
hash()
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.
Type parameters
• T
Parameters
• value: T
• hash?: Field
Returns
Hashed\<T>