Struct Finite 

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

Proof that a float is finite (neither NaN nor ±∞).

Spent by a total order: Finite<T> implements Ord/Eq, which bare f32/f64 can’t (NaN breaks reflexivity and trichotomy). With NaN gone, partial_cmp is always Some, so sorting / min/max / BTreeMap keys are total. repr(transparent); no new_ct (floats are outside the CT model).

use const_num_traits::Finite;

let a = Finite::<f64>::new(1.0).unwrap();
let b = Finite::<f64>::new(2.0).unwrap();
assert!(a < b);
assert_eq!(a.max(b).get(), 2.0);
assert!(Finite::<f64>::new(f64::NAN).is_none());
assert!(Finite::<f64>::new(f64::INFINITY).is_none());

Implementations

impl Finite<f32>

pub const fn new(value: f32) -> Option<Self>

Some iff value is finite (not NaN, not ±∞).

const fn: finiteness is a bit test — the exponent field is not all-ones — which sidesteps the non-const is_finite.

pub const unsafe fn new_unchecked(value: f32) -> Self

Safety

value must be finite.

pub const fn get(self) -> f32

The proven-finite value.

pub fn from_ref(value: &f32) -> Option<&Self>

Zero-cost borrowed proof (repr(transparent) reinterpret).

impl Finite<f64>

pub const fn new(value: f64) -> Option<Self>

Some iff value is finite (not NaN, not ±∞).

const fn: finiteness is a bit test — the exponent field is not all-ones — which sidesteps the non-const is_finite.

Examples found in repository

examples/typestates.rs (line 118)

fn finite_floats() {
    let raw = [2.0f64, f64::NAN, 1.0, f64::INFINITY, 0.5];

    // keep only the finite values; each carries its proof
    let mut xs: Vec<Finite<f64>> = raw.iter().copied().filter_map(Finite::<f64>::new).collect();
    xs.sort(); // total Ord — no `partial_cmp().unwrap()`
    let sorted: Vec<f64> = xs.iter().map(|f| f.get()).collect();
    assert_eq!(sorted, [0.5, 1.0, 2.0]);

    // finite floats as map keys
    let mut table: BTreeMap<Finite<f64>, &str> = BTreeMap::new();
    table.insert(Finite::<f64>::new(1.0).unwrap(), "one");
    table.insert(Finite::<f64>::new(2.0).unwrap(), "two");
    assert_eq!(table.get(&Finite::<f64>::new(1.0).unwrap()), Some(&"one"));
}

pub const unsafe fn new_unchecked(value: f64) -> Self

Safety

value must be finite.

pub const fn get(self) -> f64

The proven-finite value.

Examples found in repository

examples/typestates.rs (line 113)

fn finite_floats() {
    let raw = [2.0f64, f64::NAN, 1.0, f64::INFINITY, 0.5];

    // keep only the finite values; each carries its proof
    let mut xs: Vec<Finite<f64>> = raw.iter().copied().filter_map(Finite::<f64>::new).collect();
    xs.sort(); // total Ord — no `partial_cmp().unwrap()`
    let sorted: Vec<f64> = xs.iter().map(|f| f.get()).collect();
    assert_eq!(sorted, [0.5, 1.0, 2.0]);

    // finite floats as map keys
    let mut table: BTreeMap<Finite<f64>, &str> = BTreeMap::new();
    table.insert(Finite::<f64>::new(1.0).unwrap(), "one");
    table.insert(Finite::<f64>::new(2.0).unwrap(), "two");
    assert_eq!(table.get(&Finite::<f64>::new(1.0).unwrap()), Some(&"one"));
}

pub fn from_ref(value: &f64) -> Option<&Self>

Zero-cost borrowed proof (repr(transparent) reinterpret).

Trait Implementations

impl<T: Clone> Clone for Finite<T>

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

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<T: Copy> Copy for Finite<T>

impl<T: Debug> Debug for Finite<T>

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

Formats the value using the given formatter.

impl Eq for Finite<f32>

impl Eq for Finite<f64>

impl Ord for Finite<f32>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl Ord for Finite<f64>

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Finite<f32>

fn eq(&self, other: &Self) -> 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 PartialEq for Finite<f64>

fn eq(&self, other: &Self) -> 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 PartialOrd for Finite<f32>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl PartialOrd for Finite<f64>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl TryFrom<f32> for Finite<f32>

Checked construction by value; mirrors Finite::new. The natural boundary for rejecting NaN/±∞ from external float input with ?.

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: f32) -> Result<Self, TypestateError>

Performs the conversion.

impl TryFrom<f64> for Finite<f64>

Checked construction by value; mirrors Finite::new. The natural boundary for rejecting NaN/±∞ from external float input with ?.

type Error = TypestateError

The type returned in the event of a conversion error.

fn try_from(value: f64) -> Result<Self, TypestateError>

Performs the conversion.