Enum Tri 

pub enum Tri {
    Yes,
    No,
    Unknown,
}

A three-valued answer.

Tri::Unknown means “not decided”, and every consumer must treat it as a refusal rather than a maybe-yes. There is deliberately no conversion to bool that guesses.

Variants

Yes

Definitely true.

No

Definitely false.

Unknown

Could not be decided from the pattern language.

Implementations

impl Tri

pub fn is_yes(self) -> bool

Whether this is a definite yes. Unknown is not.

pub fn is_no(self) -> bool

Whether this is a definite no. Unknown is not.

pub fn is_unknown(self) -> bool

Whether the answer is undecided.

pub fn and(self, other: Self) -> Self

Conjunction: No dominates, then Unknown.

A definite No survives an undecided sibling — if one conjunct is already false the whole thing is false regardless.

pub fn or(self, other: Self) -> Self

Disjunction: Yes dominates, then Unknown.

pub fn all(items: impl IntoIterator<Item = Self>) -> Self

Fold a sequence with Tri::and, starting from Yes.

pub fn any(items: impl IntoIterator<Item = Self>) -> Self

Fold a sequence with Tri::or, starting from No.

Trait Implementations

impl Clone for Tri

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Tri

impl Debug for Tri

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

Formats the value using the given formatter.

impl Display for Tri

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

Formats the value using the given formatter.

impl Eq for Tri

impl Hash for Tri

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Tri

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Tri