Struct cfg::usefulness::Usefulness

pub struct Usefulness<G> {
    // some fields omitted
}

Contains the information about usefulness of the grammar's rules. Useful rules are both reachable and productive.

Methods

impl<'a, G> Usefulness<&'a mut G> where G: ContextFree, &'b G: ContextFreeRef<'b, Target=G>, &'b mut G: ContextFreeMut<'b, Target=G>

fn new(grammar: &'a mut G) -> Usefulness<&'a mut G>

Analyzes usefulness of the grammar's rules. In particular, it checks for reachable and productive symbols.

fn productivity(&self, sym: Symbol) -> bool

Checks whether a symbol is productive. Can be used to determine the precise reason of a rule's unproductiveness.

fn reachable<Sr>(self, syms: Sr) -> Self where Sr: AsRef<[Symbol]>

Sets symbol reachability. Takes an array of reachable symbols.

fn all_useful(&self) -> bool

Checks whether all rules in the grammar are useful.

fn all_productive(&self) -> bool

Checks whether all rules in the grammar are productive.

impl<'a, G> Usefulness<&'a mut G> where G: ContextFree, &'a G: ContextFreeRef<'a, Target=G>, &'a mut G: ContextFreeMut<'a, Target=G>

fn useless_rules(&'a self) -> UselessRules<'a, G, &'a G::Rules>

Returns an iterator over the grammar's useless rules.

fn remove_useless_rules(&mut self)

Removes useless rules. The language represented by the grammar doesn't change.