Struct cfg::prediction::FirstSetsCollector

pub struct FirstSetsCollector<'a, G> { /* private fields */ }

Collector of FIRST sets.

Implementations

impl<'a, G> FirstSetsCollector<'a, G>where G: RuleContainer + Default, &'a G: RuleContainerRef<'a, Target = G>,

pub fn new(grammar: &'a G) -> Self

Compute all FIRST sets of the grammar.

We define a binary relation FIRST(N, S), in which N is related to S if the grammar has a production of the form N ⸬= α S β, where α is a nullable string of symbols.

We compute the transitive closure of this relation.

pub fn first_set_for_string( &self, string: &[Symbol] ) -> BTreeSet<Option<Symbol>>

Calculates a FIRST set for a string of symbols.

pub fn first_sets(&self) -> &PerSymbolSets

Returns a FIRST sets structure.