Struct YaccFirsts

pub struct YaccFirsts<StorageT> { /* private fields */ }

Firsts stores all the first sets for a given grammar. For example, given this code and grammar:

  let grm = YaccGrammar::new(YaccKind::Original(YaccOriginalActionKind::GenericParseTree), "
    S: A 'b';
    A: 'a'
     | ;").unwrap();
  let firsts = Firsts::new(&grm);

then the following assertions (and only the following assertions) about the firsts set are correct:

  assert!(firsts.is_set(grm.rule_idx("S").unwrap(), grm.token_idx("a").unwrap()));
  assert!(firsts.is_set(grm.rule_idx("S").unwrap(), grm.token_idx("b").unwrap()));
  assert!(firsts.is_set(grm.rule_idx("A").unwrap(), grm.token_idx("a").unwrap()));
  assert!(firsts.is_epsilon_set(grm.rule_idx("A").unwrap()));

Implementations

impl<StorageT: 'static + PrimInt + Unsigned> YaccFirsts<StorageT>

where usize: AsPrimitive<StorageT>,

pub fn new(grm: &YaccGrammar<StorageT>) -> Self

Generates and returns the firsts set for the given grammar.

pub fn firsts(&self, ridx: RIdx<StorageT>) -> &Vob

Return all the firsts for rule ridx.

pub fn is_set(&self, ridx: RIdx<StorageT>, tidx: TIdx<StorageT>) -> bool

Returns true if the token tidx is in the first set for rule ridx.

pub fn is_epsilon_set(&self, ridx: RIdx<StorageT>) -> bool

Returns true if the rule ridx has epsilon in its first set.

pub fn set(&mut self, ridx: RIdx<StorageT>, tidx: TIdx<StorageT>) -> bool

Ensures that the firsts bit for token tidx rule ridx is set. Returns true if it was already set, or false otherwise.

Trait Implementations

impl<StorageT: Debug> Debug for YaccFirsts<StorageT>

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

Formats the value using the given formatter.