Struct cfg::history::NullHistory

pub struct NullHistory;

A history which carries no data. All operations on NullHistory are no-op.

Trait Implementations

impl Action for NullHistory

fn no_op(&self) -> Self

Returns a history with no-op semantic action.

impl Binarize for NullHistory

fn binarize<R>(&self, _rule: &R, _depth: usize) -> Self

Returns a history. May record the binarization.

impl EliminateNulling for NullHistory

fn eliminate_nulling<R>(&self, _rule: &R, _which: BinarizedRhsSubset) -> Self

Returns a history. May record the elimination.

impl AssignPrecedence for NullHistory

fn assign_precedence<R>(&self, _rule: &R, _looseness: u32) -> Self

Returns a history. May record the precedence.

impl RewriteSequence for NullHistory

type Rewritten = Self

Must be an Action, because all created grammar rules except the topmost one will have no-op semantic action.

fn top(&self, _rhs: Symbol, _sep: Option<Symbol>, _new: &[Symbol]) -> Self

Returns a history. May record the rewrite.

fn bottom(&self, _rhs: Symbol, _sep: Option<Symbol>, _new: &[Symbol]) -> Self

Returns a history. May record the rewrite.

impl HistorySource<NullHistory> for NullHistorySource

fn build(&mut self, _lhs: Symbol, _rhs: &[Symbol]) -> NullHistory

Create a history.

impl Clone for NullHistory

fn clone(&self) -> NullHistory

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for NullHistory

impl Default for NullHistory

fn default() -> NullHistory

Returns the "default value" for a type.

impl Debug for NullHistory

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

Formats the value using the given formatter.