Struct halo2_proofs::circuit::Value

pub struct Value<V> { /* private fields */ }

A value that might exist within a circuit.

This behaves like Option<V> but differs in two key ways:

• It does not expose the enum cases, or provide an Option::unwrap equivalent. This helps to ensure that unwitnessed values correctly propagate.
• It provides pass-through implementations of common traits such as Add and Mul, for improved usability.

Implementations

impl<V> Value<V>

pub const fn unknown() -> Self

Constructs an unwitnessed value.

pub const fn known(value: V) -> Self

Constructs a known value.

Examples

use halo2_proofs::circuit::Value;

let v = Value::known(37);

pub fn as_ref(&self) -> Value<&V>

Converts from &Value<V> to Value<&V>.

pub fn as_mut(&mut self) -> Value<&mut V>

Converts from &mut Value<V> to Value<&mut V>.

pub fn assert_if_known<F: FnOnce(&V) -> bool>(&self, f: F)

Enforces an assertion on the contained value, if known.

The assertion is ignored if self is Value::unknown(). Do not try to enforce circuit constraints with this method!

Panics

Panics if f returns false.

pub fn error_if_known_and<F: FnOnce(&V) -> bool>(
    &self,
    f: F
) -> Result<(), Error>

Checks the contained value for an error condition, if known.

The error check is ignored if self is Value::unknown(). Do not try to enforce circuit constraints with this method!

pub fn map<W, F: FnOnce(V) -> W>(self, f: F) -> Value<W>

Maps a Value<V> to Value<W> by applying a function to the contained value.

pub fn and_then<W, F: FnOnce(V) -> Value<W>>(self, f: F) -> Value<W>

Returns Value::unknown() if the value is Value::unknown(), otherwise calls f with the wrapped value and returns the result.

pub fn zip<W>(self, other: Value<W>) -> Value<(V, W)>

Zips self with another Value.

If self is Value::known(s) and other is Value::known(o), this method returns Value::known((s, o)). Otherwise, Value::unknown() is returned.

impl<V, W> Value<(V, W)>

pub fn unzip(self) -> (Value<V>, Value<W>)

Unzips a value containing a tuple of two values.

If self is Value::known((a, b)), this method returns (Value::known(a), Value::known(b)). Otherwise, (Value::unknown(), Value::unknown())` is returned.

impl<V> Value<&V>

pub fn copied(self) -> Value<V>where
    V: Copy,

Maps a Value<&V> to a Value<V> by copying the contents of the value.

pub fn cloned(self) -> Value<V>where
    V: Clone,

Maps a Value<&V> to a Value<V> by cloning the contents of the value.

impl<V> Value<&mut V>

pub fn copied(self) -> Value<V>where
    V: Copy,

Maps a Value<&mut V> to a Value<V> by copying the contents of the value.

pub fn cloned(self) -> Value<V>where
    V: Clone,

Maps a Value<&mut V> to a Value<V> by cloning the contents of the value.

impl<V: Copy, const LEN: usize> Value<[V; LEN]>

pub fn transpose_array(self) -> [Value<V>; LEN]

Transposes a Value<[V; LEN]> into a [Value<V>; LEN].

Value::unknown() will be mapped to [Value::unknown(); LEN].

impl<V, I> Value<I>where
    I: IntoIterator<Item = V>,
    I::IntoIter: ExactSizeIterator,

pub fn transpose_vec(self, length: usize) -> Vec<Value<V>>

Transposes a Value<impl IntoIterator<Item = V>> into a Vec<Value<V>>.

Value::unknown() will be mapped to vec![Value::unknown(); length].

Panics

Panics if self is Value::known(values) and values.len() != length.

impl<V> Value<V>

pub fn to_field<F: Field>(&self) -> Value<Assigned<F>>where
    for<'v> Assigned<F>: From<&'v V>,

Returns the field element corresponding to this value.

pub fn into_field<F: Field>(self) -> Value<Assigned<F>>where
    V: Into<Assigned<F>>,

Returns the field element corresponding to this value.

pub fn double<F: Field>(&self) -> Value<Assigned<F>>where
    V: Borrow<Assigned<F>>,

Doubles this field element.

Examples

If you have a Value<F: Field>, convert it to Value<Assigned<F>> first:

use halo2_proofs::{circuit::Value, plonk::Assigned};

let v = Value::known(F::from(2));
let v: Value<Assigned<F>> = v.into();
v.double();

pub fn square<F: Field>(&self) -> Value<Assigned<F>>where
    V: Borrow<Assigned<F>>,

Squares this field element.

pub fn cube<F: Field>(&self) -> Value<Assigned<F>>where
    V: Borrow<Assigned<F>>,

Cubes this field element.

pub fn invert<F: Field>(&self) -> Value<Assigned<F>>where
    V: Borrow<Assigned<F>>,

Inverts this assigned value (taking the inverse of zero to be zero).

impl<F: Field> Value<Assigned<F>>

pub fn evaluate(self) -> Value<F>

Evaluates this value directly, performing an unbatched inversion if necessary.

If the denominator is zero, the returned value is zero.

Trait Implementations

impl<V, O> Add<&Value<V>> for &Value<V>where
    for<'v> &'v V: Add<Output = O>,

type Output = Value<O>

The resulting type after applying the + operator.

fn add(self, rhs: Self) -> Self::Output

Performs the + operation.

impl<V, O> Add<&Value<V>> for Value<V>where
    for<'v> V: Add<&'v V, Output = O>,

type Output = Value<O>

The resulting type after applying the + operator.

fn add(self, rhs: &Self) -> Self::Output

Performs the + operation.

impl<F: Field> Add<F> for Value<&Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the + operator.

fn add(self, rhs: F) -> Self::Output

Performs the + operation.

impl<F: Field> Add<F> for Value<Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the + operator.

fn add(self, rhs: F) -> Self::Output

Performs the + operation.

impl<V, O> Add<Value<&V>> for Value<V>where
    for<'v> V: Add<&'v V, Output = O>,

type Output = Value<O>

The resulting type after applying the + operator.

fn add(self, rhs: Value<&V>) -> Self::Output

Performs the + operation.

impl<F: Field> Add<Value<F>> for Value<&Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the + operator.

fn add(self, rhs: Value<F>) -> Self::Output

Performs the + operation.

impl<F: Field> Add<Value<F>> for Value<Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the + operator.

fn add(self, rhs: Value<F>) -> Self::Output

Performs the + operation.

impl<V, O> Add<Value<V>> for &Value<V>where
    for<'v> &'v V: Add<V, Output = O>,

type Output = Value<O>

The resulting type after applying the + operator.

fn add(self, rhs: Value<V>) -> Self::Output

Performs the + operation.

impl<V, O> Add<Value<V>> for Value<&V>where
    for<'v> &'v V: Add<V, Output = O>,

type Output = Value<O>

The resulting type after applying the + operator.

fn add(self, rhs: Value<V>) -> Self::Output

Performs the + operation.

impl<V, O> Add<Value<V>> for Value<V>where
    V: Add<Output = O>,

type Output = Value<O>

The resulting type after applying the + operator.

fn add(self, rhs: Self) -> Self::Output

Performs the + operation.

impl<V: Clone> Clone for Value<V>

fn clone(&self) -> Value<V>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<V: Debug> Debug for Value<V>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<V> Default for Value<V>

fn default() -> Self

Returns the “default value” for a type.

impl<F: Field> From<Value<F>> for Value<Assigned<F>>

fn from(value: Value<F>) -> Self

Converts to this type from the input type.

impl<A, V: FromIterator<A>> FromIterator<Value<A>> for Value<V>

fn from_iter<I: IntoIterator<Item = Value<A>>>(iter: I) -> Self

Takes each element in the Iterator: if it is Value::unknown(), no further elements are taken, and the Value::unknown() is returned. Should no Value::unknown() occur, a container of type V containing the values of each Value is returned.

impl<V, O> Mul<&Value<V>> for &Value<V>where
    for<'v> &'v V: Mul<Output = O>,

type Output = Value<O>

The resulting type after applying the * operator.

fn mul(self, rhs: Self) -> Self::Output

Performs the * operation.

impl<V, O> Mul<&Value<V>> for Value<V>where
    for<'v> V: Mul<&'v V, Output = O>,

type Output = Value<O>

The resulting type after applying the * operator.

fn mul(self, rhs: &Self) -> Self::Output

Performs the * operation.

impl<F: Field> Mul<F> for Value<&Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the * operator.

fn mul(self, rhs: F) -> Self::Output

Performs the * operation.

impl<F: Field> Mul<F> for Value<Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the * operator.

fn mul(self, rhs: F) -> Self::Output

Performs the * operation.

impl<V, O> Mul<Value<&V>> for Value<V>where
    for<'v> V: Mul<&'v V, Output = O>,

type Output = Value<O>

The resulting type after applying the * operator.

fn mul(self, rhs: Value<&V>) -> Self::Output

Performs the * operation.

impl<F: Field> Mul<Value<F>> for Value<&Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the * operator.

fn mul(self, rhs: Value<F>) -> Self::Output

Performs the * operation.

impl<F: Field> Mul<Value<F>> for Value<Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the * operator.

fn mul(self, rhs: Value<F>) -> Self::Output

Performs the * operation.

impl<V, O> Mul<Value<V>> for &Value<V>where
    for<'v> &'v V: Mul<V, Output = O>,

type Output = Value<O>

The resulting type after applying the * operator.

fn mul(self, rhs: Value<V>) -> Self::Output

Performs the * operation.

impl<V, O> Mul<Value<V>> for Value<&V>where
    for<'v> &'v V: Mul<V, Output = O>,

type Output = Value<O>

The resulting type after applying the * operator.

fn mul(self, rhs: Value<V>) -> Self::Output

Performs the * operation.

impl<V, O> Mul<Value<V>> for Value<V>where
    V: Mul<Output = O>,

type Output = Value<O>

The resulting type after applying the * operator.

fn mul(self, rhs: Self) -> Self::Output

Performs the * operation.

impl<V: Neg> Neg for Value<V>

type Output = Value<<V as Neg>::Output>

The resulting type after applying the - operator.

fn neg(self) -> Self::Output

Performs the unary - operation.

impl<V, O> Sub<&Value<V>> for &Value<V>where
    for<'v> &'v V: Sub<Output = O>,

type Output = Value<O>

The resulting type after applying the - operator.

fn sub(self, rhs: Self) -> Self::Output

Performs the - operation.

impl<V, O> Sub<&Value<V>> for Value<V>where
    for<'v> V: Sub<&'v V, Output = O>,

type Output = Value<O>

The resulting type after applying the - operator.

fn sub(self, rhs: &Self) -> Self::Output

Performs the - operation.

impl<F: Field> Sub<F> for Value<&Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the - operator.

fn sub(self, rhs: F) -> Self::Output

Performs the - operation.

impl<F: Field> Sub<F> for Value<Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the - operator.

fn sub(self, rhs: F) -> Self::Output

Performs the - operation.

impl<V, O> Sub<Value<&V>> for Value<V>where
    for<'v> V: Sub<&'v V, Output = O>,

type Output = Value<O>

The resulting type after applying the - operator.

fn sub(self, rhs: Value<&V>) -> Self::Output

Performs the - operation.

impl<F: Field> Sub<Value<F>> for Value<&Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the - operator.

fn sub(self, rhs: Value<F>) -> Self::Output

Performs the - operation.

impl<F: Field> Sub<Value<F>> for Value<Assigned<F>>

type Output = Value<Assigned<F>>

The resulting type after applying the - operator.

fn sub(self, rhs: Value<F>) -> Self::Output

Performs the - operation.

impl<V, O> Sub<Value<V>> for &Value<V>where
    for<'v> &'v V: Sub<V, Output = O>,

type Output = Value<O>

The resulting type after applying the - operator.

fn sub(self, rhs: Value<V>) -> Self::Output

Performs the - operation.

impl<V, O> Sub<Value<V>> for Value<&V>where
    for<'v> &'v V: Sub<V, Output = O>,

type Output = Value<O>

The resulting type after applying the - operator.

fn sub(self, rhs: Value<V>) -> Self::Output

Performs the - operation.

impl<V, O> Sub<Value<V>> for Value<V>where
    V: Sub<Output = O>,

type Output = Value<O>

The resulting type after applying the - operator.

fn sub(self, rhs: Self) -> Self::Output

Performs the - operation.

impl<V: Copy> Copy for Value<V>