strong-kleene

strong-kleene provides Trit, a three-valued logic value with strong Kleene semantics.

Compatibility: this crate is no_std.

Quickstart

use strong_kleene::Trit;

let a = Trit::True;
let b = Trit::Unknown;

assert_eq!(!a, Trit::False);
assert_eq!(a & b, Trit::Unknown);
assert_eq!(Trit::False | b, Trit::Unknown);
assert_eq!(a ^ Trit::False, Trit::True);

How-To

Convert from bool

use strong_kleene::Trit;

let trit_true: Trit = true.into();
let trit_false: Trit = false.into();
assert_eq!(trit_true, Trit::True);
assert_eq!(trit_false, Trit::False);

Convert into bool safely

use strong_kleene::{Trit, UnknownToBoolError};

let known = Trit::True;
let unknown = Trit::Unknown;

assert_eq!(bool::try_from(known), Ok(true));
assert_eq!(bool::try_from(unknown), Err(UnknownToBoolError));

Branch on Unknown

use strong_kleene::Trit;

let value = Trit::Unknown;

match value {
    Trit::True => {}
    Trit::False => {}
    Trit::Unknown => {}
}
assert!(value.is_unknown());

Semantics

Strong Kleene logic extends classical two-valued logic with Unknown for values that are not currently known.

Legend: F = false, U = unknown, T = true.

NOT(A)

AND(A, B)

OR(A, B)

XOR(A, B)

Reference

• Trit is the primary type and supports !, &, |, and ^.
• UnknownToBoolError is returned by bool::try_from(Trit::Unknown).