snarky-universe is a snarky standard library that provides functions for dealing with various useful objects (field elements, hashes, Merkle trees, signatures, integers).

API documentationa

module Field = {
  module type Basic = {
    type bool;

    type t;

    let size_in_bits: int;

    let (==): (t, t) => bool;

    let equal: (t, t) => bool;

    let ( * ): (t, t) => t;

    let (+): (t, t) => t;

    let (-): (t, t) => t;

    let (/): (t, t) => t;

    let mul: (t, t) => t;

    let add: (t, t) => t;

    let sub: (t, t) => t;

    let div: (t, t) => t;

    let negate: t => t;

    let sqrt: t => t;

    let square: t => t;

    let invert: t => t;

    let one: t;

    let zero: t;

    let ofString: string => t;

    let ofInt: int => t;

    let ofBits: array(bool) => t;
  };

  module type Checked = {
    include Basic;

    include Cond_intf with type bool := bool and type t := t;

    let toBits: (~length: int=?, t) => array(bool);

    let parity: (~length: int=?, t) => bool;

    let assertEqual: (t, t) => unit;

    let assertR1: (t, t, t) => unit;

    let isSquare: t => bool;

    /** If x is a square in the field and
    (b, y) = x;
    If b = true, then y is sqrt(x)
    If b = false, then y is a value which is not meaningful */

    let sqrtCheck: t => (t, bool);
  };

  module type Constant = {
    [@deriving yojson]
    type t;

    include Basic with type bool := bool and type t := t;

    let parity: t => bool;

    let toString: t => string;

    let toBits: t => array(bool);
  };
};

module type S = {
  module Impl: Snarky.Snark_intf.Run with type prover_state = unit;

  module Bool: {
    open Impl;

    type t = Boolean.var;

    module Constant: {
      [@deriving yojson]
      type t = bool;
    };

    let true_: t;

    let false_: t;

    let typ: Typ.t(t, bool);

    let (||): (t, t) => t;

    let (&&): (t, t) => t;

    let (!): t => t;

    let negate: t => t;

    let (==): (t, t) => t;

    let equal: (t, t) => t;

    let all: list(t) => t;

    let any: list(t) => t;

    let exactlyOne: list(t) => t;

    let assertTrue: t => unit;

    let assertFalse: t => unit;

    let assertAll: list(t) => unit;

    let assertAny: list(t) => unit;

    let assertExactlyOne: list(t) => unit;

    let assertEqual: (t, t) => unit;
  };

  module Field: {
    include Field.Checked with type bool := Bool.t;

    module Constant: Field.Constant;

    let typ: Impl.Typ.t(t, Constant.t);
  };

  module Hash: {
    type t = Field.t;

    let equal: (t, t) => Bool.t;

    let assertEqual: (t, t) => unit;

    let hash: array(Field.t) => t;

    include Cond_intf with type bool := Bool.t and type t := t;

    module Constant: {
      [@deriving yojson]
      type t = Field.Constant.t;

      let hash: array(Field.Constant.t) => t;
    };

    let typ: Impl.Typ.t(t, Constant.t);
  };

  module MerkleTree: {
    open Impl;

    type t('a);

    module Index: {
      type t = array(Boolean.var);

      let typ: (~depth: int) => Typ.t(t, int);
    };

    module Path: {
      type t = array(Hash.t);

      let typ: (~depth: int) => Typ.t(t, array(Hash.Constant.t));
    };

    module MembershipProof: {
      type t_('index, 'hash) = {
        index: 'index,
        path: array('hash),
      };

      type t = t_(Index.t, Hash.t);

      module Constant: {
        [@deriving yojson]
        type t = t_(int, Hash.Constant.t);
      };

      let typ: (~depth: int) => Typ.t(t, Constant.t);

      let check:
        (t, Hash.t /* root hash */, Hash.t /* element hash */) => Bool.t;
    };

    let ofRoot: ('a => Hash.t, Hash.t) => t('a);

    module Constant: {
      type t('a);

      let root: t(_) => Hash.Constant.t;

      let ofArray: ('a => Hash.Constant.t, 'a, array('a)) => t('a);

      module MembershipProof: {
        let create: (t('a), int) => MembershipProof.Constant.t;

        type t = MembershipProof.Constant.t;

        let check: (t, Hash.Constant.t, Hash.Constant.t) => bool;
      };
    };
  };

  module Integer: {
    type t;

    let one: t;

    let ofBigint: Bigint.t => t;

    let ofInt: int => t;

    let ofString: string => t;

    let (+): (t, t) => t;

    let ( * ): (t, t) => t;

    let add: (t, t) => t;

    let mul: (t, t) => t;

    let divMod: (t, t) => (t, t);

    let equal: (t, t) => Bool.t;

    let (==): (t, t) => Bool.t;

    let (<=): (t, t) => Bool.t;

    let (>=): (t, t) => Bool.t;

    let (<): (t, t) => Bool.t;

    let (>): (t, t) => Bool.t;

    let toField: t => Field.t;

    let ofBits: array(Bool.t) => t;

    let toBits: (~length: int=?, t) => array(Bool.t);
  };

  module InputSpec: Input_spec.S with module Impl := Impl;

  let runMain:
    (
      InputSpec.t(unit => unit, unit, 'arg0 => 'computation0, 'public_input),
      (module InputSpec.Witness_intf with type t = 'witness),
      ('witness, 'arg0) => 'computation0
    ) =>
    unit;

  module Schnorr: {
    module PrivateKey: {
      type t;

      module Constant: {
        [@deriving yojson]
        type t;
      };
    };

    module PublicKey: {
      type t;

      let ofPrivateKey: PrivateKey.t => t;

      module Constant: {
        [@deriving yojson]
        type t;
      };

      let typ: Impl.Typ.t(t, Constant.t);
    };

    module Signature: {
      type t;

      module Constant: {
        [@deriving yojson]
        type t;
      };

      let typ: Impl.Typ.t(t, Constant.t);

      let check: (t, PublicKey.t, array(Field.t)) => Bool.t;
    };

    module Constant: {
      let sign:
        (PrivateKey.Constant.t, array(Field.Constant.t)) =>
        Signature.Constant.t;

      let check:
        (
          Signature.Constant.t,
          PublicKey.Constant.t,
          array(Field.Constant.t)
        ) =>
        bool;
    };
  };
};

module type Cond_intf = {
  type bool;

  type t;

  type cond;

  let (-?): (bool, t) => cond;

  let (-:): (cond, t) => t;
};

"Constant" module patterna

Most modules in snarky-universe have a submodule called "Constant". For example, there is a module Field with the submodule Field.Constant.

Field provides operations on "in SNARK" variable field elements, whereas Field.Constant provides operations on regular old field elements.

The difference is the following. The only things you can fundamentally do with "in snark" field elements is add and multiply them. With "Constant" field elements, you can look at their bits, turn them into a string, print them out to the console, etc.