Struct Odd 

pub struct Odd<T>(/* private fields */);

Proof that a value is odd.

A bare typestate: it carries the proof but has no consuming op in this crate. It ships here because that is where its predicate (Parity) lives. Note that Odd also implies non-zero — zero is even — so it doubles as a “non-zero and odd” proof without a separate OddNonZero type.

Implementations

impl<T: CtParity + Copy> Odd<T>

pub fn new_ct(value: T) -> CtOption<Odd<T>>

Available on crate feature ct only.

Constant-time new: None-masked when value is even.

Examples found in repository

examples/typestates.rs (line 131)

fn constant_time() {
    use const_num_traits::CtNonZero; // brings `into_nonzero_ct` into scope

    // no `bool` is produced from the secret; the option is masked
    assert!(bool::from(Odd::<u64>::new_ct(0xABCD_1235).is_some()));
    assert!(bool::from(Odd::<u64>::new_ct(0xABCD_1234).is_none()));
    assert!(bool::from(42u32.into_nonzero_ct().is_some()));
    assert!(bool::from(0u32.into_nonzero_ct().is_none()));
}

impl<T> Odd<T>

pub const unsafe fn new_unchecked(value: T) -> Self

Safety

value must be odd.

pub fn get(self) -> T

The proven-odd value.

Examples found in repository

examples/typestates.rs (line 99)

fn odd_modulus() {
    // a parsed/odd modulus, proven once
    let m = Odd::<u64>::new(0xFFFF_FFFF_FFFF_FFC5).expect("a large odd prime");
    // `Odd ⇒ non-zero` (zero is even), so this one proof covers both the
    // "odd" and "non-zero" preconditions at once.
    assert_eq!(m.get() & 1, 1);

    assert!(Odd::<u64>::new(0).is_none()); // zero is even
    assert!(Odd::<u64>::new(10).is_none());
}

impl<T: Parity + Copy> Odd<T>

pub fn new(value: T) -> Option<Self>

where T: Parity,

Some iff value is odd. const-callable on nightly when T: [const] Parity, so a const modulus can be proven odd in a const block (no runtime panic path); plain on stable.

Examples found in repository

examples/typestates.rs (line 96)

fn odd_modulus() {
    // a parsed/odd modulus, proven once
    let m = Odd::<u64>::new(0xFFFF_FFFF_FFFF_FFC5).expect("a large odd prime");
    // `Odd ⇒ non-zero` (zero is even), so this one proof covers both the
    // "odd" and "non-zero" preconditions at once.
    assert_eq!(m.get() & 1, 1);

    assert!(Odd::<u64>::new(0).is_none()); // zero is even
    assert!(Odd::<u64>::new(10).is_none());
}

impl<T> Odd<T>

where for<'a> &'a T: Parity,

pub fn from_ref(value: &T) -> Option<&Self>

Zero-cost borrowed proof — relies on the blanket impl Parity for &T (for Copy T) or a non-Copy type’s own Parity for &Self.

Trait Implementations

impl<T> AsRef<T> for Odd<T>

Borrows the proven-odd value without consuming the proof.

fn as_ref(&self) -> &T

Converts this type into a shared reference of the (usually inferred) input type.

impl<T: Clone> Clone for Odd<T>

fn clone(&self) -> Odd<T>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Copy> Copy for Odd<T>

impl<T: Debug> Debug for Odd<T>

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

Formats the value using the given formatter.

impl<T: Eq> Eq for Odd<T>

impl<T: PartialEq> PartialEq for Odd<T>

fn eq(&self, other: &Odd<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: PartialEq> StructuralPartialEq for Odd<T>

impl TryFrom<i8> for Odd<i8>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: i8) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<i16> for Odd<i16>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: i16) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<i32> for Odd<i32>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: i32) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<i64> for Odd<i64>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: i64) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<i128> for Odd<i128>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: i128) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<isize> for Odd<isize>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: isize) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<u8> for Odd<u8>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: u8) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<u16> for Odd<u16>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: u16) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<u32> for Odd<u32>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: u32) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<u64> for Odd<u64>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: u64) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<u128> for Odd<u128>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: u128) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<usize> for Odd<usize>

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: usize) -> Result<Self, TypestateError>

Performs the conversion.