Struct cfg::classification::useful::Usefulness

pub struct Usefulness<G> { /* 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>, 

pub 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.

pub 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.

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

Sets symbol reachability. Takes an array of reachable symbols.

pub fn all_useful(&self) -> bool

Checks whether all rules in the grammar are useful.

pub 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>, 

Important traits for UselessRules<'a, G, <&'a G as ContextFreeRef<'a>>::Rules>

impl<'a, G> Iterator for UselessRules<'a, G, <&'a G as ContextFreeRef<'a>>::Rules> where
    G: ContextFree + 'a,
    &'a G: ContextFreeRef<'a, Target = G>,  type Item = UselessRule<<<&'a G as ContextFreeRef<'a>>::Rules as Iterator>::Item>;

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

Returns an iterator over the grammar's useless rules.

pub fn remove_useless_rules(&mut self)

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