Struct FirstFollowSets 

pub struct FirstFollowSets<'a> {
    pub grammar: &'a ContextFreeGrammar,
    pub first: Vec<HashSet<Option<usize>>>,
    pub follow: Vec<HashSet<Option<usize>>>,
}

Computes FIRST and FOLLOW sets for a context-free grammar.

Fields

grammar: &'a ContextFreeGrammar

The grammar.

first: Vec<HashSet<Option<usize>>>

FIRST sets: nonterminal index → set of (Option<terminal_index>) None represents ε.

follow: Vec<HashSet<Option<usize>>>

FOLLOW sets: nonterminal index → set of (Option<terminal_index>) None represents end-of-input ($).

Implementations

impl<'a> FirstFollowSets<'a>

pub fn compute(grammar: &'a ContextFreeGrammar) -> Self

Compute FIRST and FOLLOW sets for the grammar.

pub fn get_first(&self, nt: usize) -> &HashSet<Option<usize>>

Get FIRST set for a nonterminal.

pub fn get_follow(&self, nt: usize) -> &HashSet<Option<usize>>

Get FOLLOW set for a nonterminal.

pub fn is_nullable(&self, nt: usize) -> bool

Check if a nonterminal is nullable (ε ∈ FIRST(nt)).