/rust/registry/src/index.crates.io-1949cf8c6b5b557f/num-traits-0.2.19/src/identities.rs

Source
use core::num::Wrapping;
use core::ops::{Add, Mul};

/// Defines an additive identity element for `Self`.
///
/// # Laws
///
/// ```text
/// a + 0 = a       ∀ a ∈ Self
/// 0 + a = a       ∀ a ∈ Self
/// ```
pub trait Zero: Sized + Add<Self, Output = Self> {
    /// Returns the additive identity element of `Self`, `0`.
    /// # Purity
    ///
    /// This function should return the same result at all times regardless of
    /// external mutable state, for example values stored in TLS or in
    /// `static mut`s.
    // This cannot be an associated constant, because of bignums.
    fn zero() -> Self;

    /// Sets `self` to the additive identity element of `Self`, `0`.
    fn set_zero(&mut self) {
        *self = Zero::zero();
    }

    /// Returns `true` if `self` is equal to the additive identity.
    fn is_zero(&self) -> bool;
}

/// Defines an associated constant representing the additive identity element
/// for `Self`.
pub trait ConstZero: Zero {
    /// The additive identity element of `Self`, `0`.
    const ZERO: Self;
}

macro_rules! zero_impl {
    ($t:ty, $v:expr) => {
        impl Zero for $t {
            #[inline]
            fn zero() -> $t {
                $v
            }
            #[inline]
            fn is_zero(&self) -> bool {
                *self == $v
            }
        }

        impl ConstZero for $t {
            const ZERO: Self = $v;
        }
    };
}

zero_impl!(usize, 0);
zero_impl!(u8, 0);
zero_impl!(u16, 0);
zero_impl!(u32, 0);
zero_impl!(u64, 0);
zero_impl!(u128, 0);

zero_impl!(isize, 0);
zero_impl!(i8, 0);
zero_impl!(i16, 0);
zero_impl!(i32, 0);
zero_impl!(i64, 0);
zero_impl!(i128, 0);

zero_impl!(f32, 0.0);
zero_impl!(f64, 0.0);

impl<T: Zero> Zero for Wrapping<T>
where
    Wrapping<T>: Add<Output = Wrapping<T>>,
{
    fn is_zero(&self) -> bool {
        self.0.is_zero()
    }

    fn set_zero(&mut self) {
        self.0.set_zero();
    }

    fn zero() -> Self {
        Wrapping(T::zero())
    }
}

impl<T: ConstZero> ConstZero for Wrapping<T>
where
    Wrapping<T>: Add<Output = Wrapping<T>>,
{
    const ZERO: Self = Wrapping(T::ZERO);
}

/// Defines a multiplicative identity element for `Self`.
///
/// # Laws
///
/// ```text
/// a * 1 = a       ∀ a ∈ Self
/// 1 * a = a       ∀ a ∈ Self
/// ```
pub trait One: Sized + Mul<Self, Output = Self> {
    /// Returns the multiplicative identity element of `Self`, `1`.
    ///
    /// # Purity
    ///
    /// This function should return the same result at all times regardless of
    /// external mutable state, for example values stored in TLS or in
    /// `static mut`s.
    // This cannot be an associated constant, because of bignums.
    fn one() -> Self;

    /// Sets `self` to the multiplicative identity element of `Self`, `1`.
    fn set_one(&mut self) {
        *self = One::one();
    }

    /// Returns `true` if `self` is equal to the multiplicative identity.
    ///
    /// For performance reasons, it's best to implement this manually.
    /// After a semver bump, this method will be required, and the
    /// `where Self: PartialEq` bound will be removed.
    #[inline]
    fn is_one(&self) -> bool
    where
        Self: PartialEq,
    {
        *self == Self::one()
    }
}

/// Defines an associated constant representing the multiplicative identity
/// element for `Self`.
pub trait ConstOne: One {
    /// The multiplicative identity element of `Self`, `1`.
    const ONE: Self;
}

macro_rules! one_impl {
    ($t:ty, $v:expr) => {
        impl One for $t {
            #[inline]
            fn one() -> $t {
                $v
            }
            #[inline]
            fn is_one(&self) -> bool {
                *self == $v
            }
        }

        impl ConstOne for $t {
            const ONE: Self = $v;
        }
    };
}

one_impl!(usize, 1);
one_impl!(u8, 1);
one_impl!(u16, 1);
one_impl!(u32, 1);
one_impl!(u64, 1);
one_impl!(u128, 1);

one_impl!(isize, 1);
one_impl!(i8, 1);
one_impl!(i16, 1);
one_impl!(i32, 1);
one_impl!(i64, 1);
one_impl!(i128, 1);

one_impl!(f32, 1.0);
one_impl!(f64, 1.0);

impl<T: One> One for Wrapping<T>
where
    Wrapping<T>: Mul<Output = Wrapping<T>>,
{
    fn set_one(&mut self) {
        self.0.set_one();
    }

    fn one() -> Self {
        Wrapping(T::one())
    }
}

impl<T: ConstOne> ConstOne for Wrapping<T>
where
    Wrapping<T>: Mul<Output = Wrapping<T>>,
{
    const ONE: Self = Wrapping(T::ONE);
}

// Some helper functions provided for backwards compatibility.

/// Returns the additive identity, `0`.
#[inline(always)]
pub fn zero<T: Zero>() -> T {
    Zero::zero()
}

/// Returns the multiplicative identity, `1`.
#[inline(always)]
pub fn one<T: One>() -> T {
    One::one()
}

#[test]
fn wrapping_identities() {
    macro_rules! test_wrapping_identities {
        ($($t:ty)+) => {
            $(
                assert_eq!(zero::<$t>(), zero::<Wrapping<$t>>().0);
                assert_eq!(one::<$t>(), one::<Wrapping<$t>>().0);
                assert_eq!((0 as $t).is_zero(), Wrapping(0 as $t).is_zero());
                assert_eq!((1 as $t).is_zero(), Wrapping(1 as $t).is_zero());
            )+
        };
    }

    test_wrapping_identities!(isize i8 i16 i32 i64 usize u8 u16 u32 u64);
}

#[test]
fn wrapping_is_zero() {
    fn require_zero<T: Zero>(_: &T) {}
    require_zero(&Wrapping(42));
}
#[test]
fn wrapping_is_one() {
    fn require_one<T: One>(_: &T) {}
    require_one(&Wrapping(42));
}

Coverage Report

Created: 2025-10-28 06:23

Line	Count	Source
1		use core::num::Wrapping;
2		use core::ops::{Add, Mul};
3
4		/// Defines an additive identity element for `Self`.
5		///
6		/// # Laws
7		///
8		/// ```text
9		/// a + 0 = a ∀ a ∈ Self
10		/// 0 + a = a ∀ a ∈ Self
11		/// ```
12		pub trait Zero: Sized + Add<Self, Output = Self> {
13		/// Returns the additive identity element of `Self`, `0`.
14		/// # Purity
15		///
16		/// This function should return the same result at all times regardless of
17		/// external mutable state, for example values stored in TLS or in
18		/// `static mut`s.
19		// This cannot be an associated constant, because of bignums.
20		fn zero() -> Self;
21
22		/// Sets `self` to the additive identity element of `Self`, `0`.
23	0	fn set_zero(&mut self) {
24	0	*self = Zero::zero();
25	0	}
26
27		/// Returns `true` if `self` is equal to the additive identity.
28		fn is_zero(&self) -> bool;
29		}
30
31		/// Defines an associated constant representing the additive identity element
32		/// for `Self`.
33		pub trait ConstZero: Zero {
34		/// The additive identity element of `Self`, `0`.
35		const ZERO: Self;
36		}
37
38		macro_rules! zero_impl {
39		($t:ty, $v:expr) => {
40		impl Zero for $t {
41		#[inline]
42	0	fn zero() -> $t {
43		$v
44	0	} Unexecuted instantiation: <usize as num_traits::identities::Zero>::zero Unexecuted instantiation: <u32 as num_traits::identities::Zero>::zero Unexecuted instantiation: <u64 as num_traits::identities::Zero>::zero Unexecuted instantiation: <i32 as num_traits::identities::Zero>::zero Unexecuted instantiation: <usize as num_traits::identities::Zero>::zero Unexecuted instantiation: <u8 as num_traits::identities::Zero>::zero Unexecuted instantiation: <u16 as num_traits::identities::Zero>::zero Unexecuted instantiation: <u32 as num_traits::identities::Zero>::zero Unexecuted instantiation: <u64 as num_traits::identities::Zero>::zero Unexecuted instantiation: <u128 as num_traits::identities::Zero>::zero Unexecuted instantiation: <isize as num_traits::identities::Zero>::zero Unexecuted instantiation: <i8 as num_traits::identities::Zero>::zero Unexecuted instantiation: <i16 as num_traits::identities::Zero>::zero Unexecuted instantiation: <i32 as num_traits::identities::Zero>::zero Unexecuted instantiation: <i64 as num_traits::identities::Zero>::zero Unexecuted instantiation: <i128 as num_traits::identities::Zero>::zero Unexecuted instantiation: <f32 as num_traits::identities::Zero>::zero Unexecuted instantiation: <f64 as num_traits::identities::Zero>::zero
45		#[inline]
46	0	fn is_zero(&self) -> bool {
47	0	*self == $v
48	0	} Unexecuted instantiation: <u8 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <u32 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <u64 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <f64 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <usize as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <u8 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <u16 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <u32 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <u64 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <u128 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <isize as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <i8 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <i16 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <i32 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <i64 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <i128 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <f32 as num_traits::identities::Zero>::is_zero Unexecuted instantiation: <f64 as num_traits::identities::Zero>::is_zero
49		}
50
51		impl ConstZero for $t {
52		const ZERO: Self = $v;
53		}
54		};
55		}
56
57		zero_impl!(usize, 0);
58		zero_impl!(u8, 0);
59		zero_impl!(u16, 0);
60		zero_impl!(u32, 0);
61		zero_impl!(u64, 0);
62		zero_impl!(u128, 0);
63
64		zero_impl!(isize, 0);
65		zero_impl!(i8, 0);
66		zero_impl!(i16, 0);
67		zero_impl!(i32, 0);
68		zero_impl!(i64, 0);
69		zero_impl!(i128, 0);
70
71		zero_impl!(f32, 0.0);
72		zero_impl!(f64, 0.0);
73
74		impl<T: Zero> Zero for Wrapping<T>
75		where
76		Wrapping<T>: Add<Output = Wrapping<T>>,
77		{
78	0	fn is_zero(&self) -> bool {
79	0	self.0.is_zero()
80	0	}
81
82	0	fn set_zero(&mut self) {
83	0	self.0.set_zero();
84	0	}
85
86	0	fn zero() -> Self {
87	0	Wrapping(T::zero())
88	0	}
89		}
90
91		impl<T: ConstZero> ConstZero for Wrapping<T>
92		where
93		Wrapping<T>: Add<Output = Wrapping<T>>,
94		{
95		const ZERO: Self = Wrapping(T::ZERO);
96		}
97
98		/// Defines a multiplicative identity element for `Self`.
99		///
100		/// # Laws
101		///
102		/// ```text
103		/// a * 1 = a ∀ a ∈ Self
104		/// 1 * a = a ∀ a ∈ Self
105		/// ```
106		pub trait One: Sized + Mul<Self, Output = Self> {
107		/// Returns the multiplicative identity element of `Self`, `1`.
108		///
109		/// # Purity
110		///
111		/// This function should return the same result at all times regardless of
112		/// external mutable state, for example values stored in TLS or in
113		/// `static mut`s.
114		// This cannot be an associated constant, because of bignums.
115		fn one() -> Self;
116
117		/// Sets `self` to the multiplicative identity element of `Self`, `1`.
118	0	fn set_one(&mut self) {
119	0	*self = One::one();
120	0	}
121
122		/// Returns `true` if `self` is equal to the multiplicative identity.
123		///
124		/// For performance reasons, it's best to implement this manually.
125		/// After a semver bump, this method will be required, and the
126		/// `where Self: PartialEq` bound will be removed.
127		#[inline]
128	0	fn is_one(&self) -> bool
129	0	where
130	0	Self: PartialEq,
131		{
132	0	*self == Self::one()
133	0	}
134		}
135
136		/// Defines an associated constant representing the multiplicative identity
137		/// element for `Self`.
138		pub trait ConstOne: One {
139		/// The multiplicative identity element of `Self`, `1`.
140		const ONE: Self;
141		}
142
143		macro_rules! one_impl {
144		($t:ty, $v:expr) => {
145		impl One for $t {
146		#[inline]
147	0	fn one() -> $t {
148		$v
149	0	} Unexecuted instantiation: <u32 as num_traits::identities::One>::one Unexecuted instantiation: <u64 as num_traits::identities::One>::one Unexecuted instantiation: <u128 as num_traits::identities::One>::one Unexecuted instantiation: <usize as num_traits::identities::One>::one Unexecuted instantiation: <u8 as num_traits::identities::One>::one Unexecuted instantiation: <u16 as num_traits::identities::One>::one Unexecuted instantiation: <u32 as num_traits::identities::One>::one Unexecuted instantiation: <u64 as num_traits::identities::One>::one Unexecuted instantiation: <u128 as num_traits::identities::One>::one Unexecuted instantiation: <isize as num_traits::identities::One>::one Unexecuted instantiation: <i8 as num_traits::identities::One>::one Unexecuted instantiation: <i16 as num_traits::identities::One>::one Unexecuted instantiation: <i32 as num_traits::identities::One>::one Unexecuted instantiation: <i64 as num_traits::identities::One>::one Unexecuted instantiation: <i128 as num_traits::identities::One>::one Unexecuted instantiation: <f32 as num_traits::identities::One>::one Unexecuted instantiation: <f64 as num_traits::identities::One>::one Unexecuted instantiation: <usize as num_traits::identities::One>::one Unexecuted instantiation: <u8 as num_traits::identities::One>::one Unexecuted instantiation: <u16 as num_traits::identities::One>::one
150		#[inline]
151	0	fn is_one(&self) -> bool {
152	0	*self == $v
153	0	} Unexecuted instantiation: <u64 as num_traits::identities::One>::is_one Unexecuted instantiation: <u32 as num_traits::identities::One>::is_one Unexecuted instantiation: <u64 as num_traits::identities::One>::is_one Unexecuted instantiation: <u128 as num_traits::identities::One>::is_one Unexecuted instantiation: <isize as num_traits::identities::One>::is_one Unexecuted instantiation: <i8 as num_traits::identities::One>::is_one Unexecuted instantiation: <i16 as num_traits::identities::One>::is_one Unexecuted instantiation: <i32 as num_traits::identities::One>::is_one Unexecuted instantiation: <i64 as num_traits::identities::One>::is_one Unexecuted instantiation: <i128 as num_traits::identities::One>::is_one Unexecuted instantiation: <f32 as num_traits::identities::One>::is_one Unexecuted instantiation: <f64 as num_traits::identities::One>::is_one Unexecuted instantiation: <usize as num_traits::identities::One>::is_one Unexecuted instantiation: <u8 as num_traits::identities::One>::is_one Unexecuted instantiation: <u16 as num_traits::identities::One>::is_one
154		}
155
156		impl ConstOne for $t {
157		const ONE: Self = $v;
158		}
159		};
160		}
161
162		one_impl!(usize, 1);
163		one_impl!(u8, 1);
164		one_impl!(u16, 1);
165		one_impl!(u32, 1);
166		one_impl!(u64, 1);
167		one_impl!(u128, 1);
168
169		one_impl!(isize, 1);
170		one_impl!(i8, 1);
171		one_impl!(i16, 1);
172		one_impl!(i32, 1);
173		one_impl!(i64, 1);
174		one_impl!(i128, 1);
175
176		one_impl!(f32, 1.0);
177		one_impl!(f64, 1.0);
178
179		impl<T: One> One for Wrapping<T>
180		where
181		Wrapping<T>: Mul<Output = Wrapping<T>>,
182		{
183	0	fn set_one(&mut self) {
184	0	self.0.set_one();
185	0	}
186
187	0	fn one() -> Self {
188	0	Wrapping(T::one())
189	0	}
190		}
191
192		impl<T: ConstOne> ConstOne for Wrapping<T>
193		where
194		Wrapping<T>: Mul<Output = Wrapping<T>>,
195		{
196		const ONE: Self = Wrapping(T::ONE);
197		}
198
199		// Some helper functions provided for backwards compatibility.
200
201		/// Returns the additive identity, `0`.
202		#[inline(always)]
203	0	pub fn zero<T: Zero>() -> T {
204	0	Zero::zero()
205	0	}
206
207		/// Returns the multiplicative identity, `1`.
208		#[inline(always)]
209	0	pub fn one<T: One>() -> T {
210	0	One::one()
211	0	}
212
213		#[test]
214		fn wrapping_identities() {
215		macro_rules! test_wrapping_identities {
216		($($t:ty)+) => {
217		$(
218		assert_eq!(zero::<$t>(), zero::<Wrapping<$t>>().0);
219		assert_eq!(one::<$t>(), one::<Wrapping<$t>>().0);
220		assert_eq!((0 as $t).is_zero(), Wrapping(0 as $t).is_zero());
221		assert_eq!((1 as $t).is_zero(), Wrapping(1 as $t).is_zero());
222		)+
223		};
224		}
225
226		test_wrapping_identities!(isize i8 i16 i32 i64 usize u8 u16 u32 u64);
227		}
228
229		#[test]
230		fn wrapping_is_zero() {
231		fn require_zero<T: Zero>(_: &T) {}
232		require_zero(&Wrapping(42));
233		}
234		#[test]
235		fn wrapping_is_one() {
236		fn require_one<T: One>(_: &T) {}
237		require_one(&Wrapping(42));
238		}