Struct halo2_proofs::circuit::Region

pub struct Region<'r, F: Field> { /* private fields */ }

A region of the circuit in which a Chip can assign cells.

Inside a region, the chip may freely use relative offsets; the Layouter will treat these assignments as a single “region” within the circuit.

The Layouter is allowed to optimise between regions as it sees fit. Chips must use Region::constrain_equal to copy in variables assigned in other regions.

TODO: It would be great if we could constrain the columns in these types to be “logical” columns that are guaranteed to correspond to the chip (and have come from Chip::Config).

Implementations

impl<'r, F: Field> Region<'r, F>

pub fn assign_advice<'v, V, VR, A, AR>(
    &'v mut self,
    annotation: A,
    column: Column<Advice>,
    offset: usize,
    to: V
) -> Result<AssignedCell<VR, F>, Error> where
    V: FnMut() -> Result<VR, Error> + 'v,
    for<'vr> Assigned<F>: From<&'vr VR>,
    A: Fn() -> AR,
    AR: Into<String>, 

Assign an advice column value (witness).

Even though to has FnMut bounds, it is guaranteed to be called at most once.

pub fn assign_advice_from_constant<VR, A, AR>(
    &mut self,
    annotation: A,
    column: Column<Advice>,
    offset: usize,
    constant: VR
) -> Result<AssignedCell<VR, F>, Error> where
    for<'vr> Assigned<F>: From<&'vr VR>,
    A: Fn() -> AR,
    AR: Into<String>, 

Assigns a constant value to the column advice at offset within this region.

The constant value will be assigned to a cell within one of the fixed columns configured via ConstraintSystem::enable_constant.

Returns the advice cell.

pub fn assign_advice_from_instance<A, AR>(
    &mut self,
    annotation: A,
    instance: Column<Instance>,
    row: usize,
    advice: Column<Advice>,
    offset: usize
) -> Result<AssignedCell<F, F>, Error> where
    A: Fn() -> AR,
    AR: Into<String>, 

Assign the value of the instance column’s cell at absolute location row to the column advice at offset within this region.

Returns the advice cell, and its value if known.

pub fn assign_fixed<'v, V, VR, A, AR>(
    &'v mut self,
    annotation: A,
    column: Column<Fixed>,
    offset: usize,
    to: V
) -> Result<AssignedCell<VR, F>, Error> where
    V: FnMut() -> Result<VR, Error> + 'v,
    for<'vr> Assigned<F>: From<&'vr VR>,
    A: Fn() -> AR,
    AR: Into<String>, 

Assign a fixed value.

Even though to has FnMut bounds, it is guaranteed to be called at most once.

pub fn constrain_constant<VR>(
    &mut self,
    cell: Cell,
    constant: VR
) -> Result<(), Error> where
    VR: Into<Assigned<F>>, 

Constrains a cell to have a constant value.

Returns an error if the cell is in a column where equality has not been enabled.

pub fn constrain_equal(&mut self, left: Cell, right: Cell) -> Result<(), Error>

Constrains two cells to have the same value.

Returns an error if either of the cells are in columns where equality has not been enabled.

Trait Implementations

impl<'r, F: Debug + Field> Debug for Region<'r, F>

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

Formats the value using the given formatter.

impl<'r, F: Field> From<&'r mut (dyn RegionLayouter<F> + 'r)> for Region<'r, F>

fn from(region: &'r mut dyn RegionLayouter<F>) -> Self

Converts to this type from the input type.