Enum EngineUnknownReason 

pub enum EngineUnknownReason {
    CycleCut,
    IncompleteKnowledge,
    NafDependent,
    BackendUnavailable,
    NonFinite,
}

Why the engine cannot currently return a definitive True or False.

Variants

CycleCut

Search encountered a recursive cycle and cut it rather than diverging.

IncompleteKnowledge

Result depends on knowledge the current KB does not have yet.

NafDependent

Result depends on negation-as-failure and is therefore not classically proved.

BackendUnavailable

An external compute predicate could not be evaluated because its backend was unreachable or unregistered — the result is genuinely undetermined, NOT false.

NonFinite

A numeric operand or computed result is non-finite (±inf/NaN) — e.g. a literal too large for an f64 (~309+ digits overflows to ±inf). The comparison/arithmetic is genuinely undetermined, NOT a confident TRUE/FALSE.

Trait Implementations

impl Clone for UnknownReason

fn clone(&self) -> UnknownReason

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for UnknownReason

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

Formats the value using the given formatter.

impl Eq for UnknownReason

impl PartialEq for UnknownReason

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for UnknownReason