num_primitive/
number.rs

1use crate::{PrimitiveBytes, PrimitiveError};
2
3trait Sealed {}
4struct SealedToken;
5
6/// Trait for all primitive [numeric types].
7///
8/// This encapsulates trait implementations and inherent methods that are common among all of the
9/// primitive numeric types: [`f32`], [`f64`], [`i8`], [`i16`], [`i32`], [`i64`], [`i128`],
10/// [`isize`], [`u8`], [`u16`], [`u32`], [`u64`], [`u128`], and [`usize`]. Unstable types like
11/// [`f16`] and [`f128`] will be added once they are stabilized.
12///
13/// See the corresponding items on the individual types for more documentation and examples.
14///
15/// This trait is sealed with a private trait to prevent downstream implementations, so we may
16/// continue to expand along with the standard library without worrying about breaking changes for
17/// implementors.
18///
19/// [numeric types]: https://doc.rust-lang.org/reference/types/numeric.html
20///
21/// # Examples
22///
23/// ```
24/// use num_primitive::{PrimitiveNumber, PrimitiveNumberRef};
25///
26/// fn dot_product<T: PrimitiveNumber>(a: &[T], b: &[T]) -> T {
27///     assert_eq!(a.len(), b.len());
28///     // Note that we have to dereference to use `T: Mul<&T>`
29///     core::iter::zip(a, b).map(|(a, b)| (*a) * b).sum()
30/// }
31///
32/// fn dot_product_ref<T>(a: &[T], b: &[T]) -> T
33/// where
34///     T: PrimitiveNumber,
35///     for<'a> &'a T: PrimitiveNumberRef<T>,
36/// {
37///     assert_eq!(a.len(), b.len());
38///     // In this case we can use `&T: Mul`
39///     core::iter::zip(a, b).map(|(a, b)| a * b).sum()
40/// }
41///
42/// assert_eq!(dot_product::<i32>(&[1, 3, -5], &[4, -2, -1]), 3);
43/// assert_eq!(dot_product_ref::<f64>(&[1., 3., -5.], &[4., -2., -1.]), 3.);
44/// ```
45#[expect(private_bounds)]
46pub trait PrimitiveNumber:
47    'static
48    + Sealed
49    + PrimitiveNumberAs<f32>
50    + PrimitiveNumberAs<f64>
51    + PrimitiveNumberAs<i8>
52    + PrimitiveNumberAs<i16>
53    + PrimitiveNumberAs<i32>
54    + PrimitiveNumberAs<i64>
55    + PrimitiveNumberAs<i128>
56    + PrimitiveNumberAs<isize>
57    + PrimitiveNumberAs<u8>
58    + PrimitiveNumberAs<u16>
59    + PrimitiveNumberAs<u32>
60    + PrimitiveNumberAs<u64>
61    + PrimitiveNumberAs<u128>
62    + PrimitiveNumberAs<usize>
63    + core::cmp::PartialEq
64    + core::cmp::PartialOrd
65    + core::convert::From<bool>
66    + core::default::Default
67    + core::fmt::Debug
68    + core::fmt::Display
69    + core::fmt::LowerExp
70    + core::fmt::UpperExp
71    + core::iter::Product<Self>
72    + core::iter::Sum<Self>
73    + core::marker::Copy
74    + core::marker::Send
75    + core::marker::Sync
76    + core::marker::Unpin
77    + core::ops::Add<Self, Output = Self>
78    + core::ops::AddAssign<Self>
79    + core::ops::Div<Self, Output = Self>
80    + core::ops::DivAssign<Self>
81    + core::ops::Mul<Self, Output = Self>
82    + core::ops::MulAssign<Self>
83    + core::ops::Rem<Self, Output = Self>
84    + core::ops::RemAssign<Self>
85    + core::ops::Sub<Self, Output = Self>
86    + core::ops::SubAssign<Self>
87    + core::panic::RefUnwindSafe
88    + core::panic::UnwindSafe
89    + core::str::FromStr<Err: PrimitiveError>
90    + for<'a> core::iter::Product<&'a Self>
91    + for<'a> core::iter::Sum<&'a Self>
92    + for<'a> core::ops::Add<&'a Self, Output = Self>
93    + for<'a> core::ops::AddAssign<&'a Self>
94    + for<'a> core::ops::Div<&'a Self, Output = Self>
95    + for<'a> core::ops::DivAssign<&'a Self>
96    + for<'a> core::ops::Mul<&'a Self, Output = Self>
97    + for<'a> core::ops::MulAssign<&'a Self>
98    + for<'a> core::ops::Rem<&'a Self, Output = Self>
99    + for<'a> core::ops::RemAssign<&'a Self>
100    + for<'a> core::ops::Sub<&'a Self, Output = Self>
101    + for<'a> core::ops::SubAssign<&'a Self>
102{
103    /// An array of bytes used by methods like [`from_be_bytes`][Self::from_be_bytes] and
104    /// [`to_be_bytes`][Self::to_be_bytes]. It is effectively `[u8; size_of::<Self>()]`.
105    type Bytes: PrimitiveBytes;
106
107    /// Creates a number from its representation as a byte array in big endian.
108    fn from_be_bytes(bytes: Self::Bytes) -> Self;
109
110    /// Creates a number from its representation as a byte array in little endian.
111    fn from_le_bytes(bytes: Self::Bytes) -> Self;
112
113    /// Creates a number from its representation as a byte array in native endian.
114    fn from_ne_bytes(bytes: Self::Bytes) -> Self;
115
116    /// Calculates the midpoint (average) between `self` and `other`.
117    fn midpoint(self, other: Self) -> Self;
118
119    /// Returns the memory representation of this number as a byte array in little-endian order.
120    fn to_be_bytes(self) -> Self::Bytes;
121
122    /// Returns the memory representation of this number as a byte array in big-endian order.
123    fn to_le_bytes(self) -> Self::Bytes;
124
125    /// Returns the memory representation of this number as a byte array in native-endian order.
126    fn to_ne_bytes(self) -> Self::Bytes;
127
128    /// Creates a number using a type cast, `value as Self`.
129    ///
130    /// Note: unlike other `num-primitive` methods, there is no inherent method by this name on the
131    /// actual types.
132    fn as_from<T>(value: T) -> Self
133    where
134        Self: PrimitiveNumberAs<T>,
135    {
136        <Self as PrimitiveNumberAs<T>>::__as_from(value, SealedToken)
137    }
138
139    /// Converts this number with a type cast, `self as T`.
140    ///
141    /// Note: unlike other `num-primitive` methods, there is no inherent method by this name on the
142    /// actual types.
143    fn as_to<T>(self) -> T
144    where
145        Self: PrimitiveNumberAs<T>,
146    {
147        <Self as PrimitiveNumberAs<T>>::__as_to(self, SealedToken)
148    }
149}
150
151/// Trait for references to primitive numbers ([`PrimitiveNumber`]).
152///
153/// This enables traits like the standard operators in generic code,
154/// e.g. `where &T: PrimitiveNumberRef<T>`.
155#[expect(private_bounds)]
156pub trait PrimitiveNumberRef<T>:
157    Sealed
158    + core::borrow::Borrow<T>
159    + core::cmp::PartialEq
160    + core::cmp::PartialOrd
161    + core::fmt::Debug
162    + core::fmt::Display
163    + core::fmt::LowerExp
164    + core::fmt::UpperExp
165    + core::marker::Copy
166    + core::marker::Send
167    + core::marker::Sync
168    + core::marker::Unpin
169    + core::ops::Add<T, Output = T>
170    + core::ops::Deref<Target = T>
171    + core::ops::Div<T, Output = T>
172    + core::ops::Mul<T, Output = T>
173    + core::ops::Rem<T, Output = T>
174    + core::ops::Sub<T, Output = T>
175    + core::panic::RefUnwindSafe
176    + core::panic::UnwindSafe
177    + for<'a> core::ops::Add<&'a T, Output = T>
178    + for<'a> core::ops::Div<&'a T, Output = T>
179    + for<'a> core::ops::Mul<&'a T, Output = T>
180    + for<'a> core::ops::Rem<&'a T, Output = T>
181    + for<'a> core::ops::Sub<&'a T, Output = T>
182{
183}
184
185/// Trait for numeric conversions supported by the [`as`] keyword.
186///
187/// This is effectively the same as the [type cast] expression `self as N`, implemented for all
188/// combinations of [`PrimitiveNumber`].
189///
190/// [`as`]: https://doc.rust-lang.org/std/keyword.as.html
191/// [type cast]: https://doc.rust-lang.org/reference/expressions/operator-expr.html#type-cast-expressions
192///
193/// # Examples
194///
195/// `PrimitiveNumberAs<{number}>` is a supertrait of [`PrimitiveNumber`] for all primitive floats
196/// and integers, so you do not need to use this trait directly when converting concrete types.
197///
198/// ```
199/// use num_primitive::PrimitiveNumber;
200///
201/// // Clamp any number to the interval 0..=100, unless it is NaN.
202/// fn clamp_percentage<Number: PrimitiveNumber>(x: Number) -> Number {
203///     let clamped = x.as_to::<f64>().clamp(0.0, 100.0);
204///     Number::as_from(clamped)
205/// }
206///
207/// assert_eq!(clamp_percentage(-42_i8), 0_i8);
208/// assert_eq!(clamp_percentage(42_u128), 42_u128);
209/// assert_eq!(clamp_percentage(1e100_f64), 100_f64);
210/// assert!(clamp_percentage(f32::NAN).is_nan());
211/// ```
212///
213/// However, if the other type is also generic, an explicit type constraint is needed.
214///
215/// ```
216/// use num_primitive::{PrimitiveNumber, PrimitiveNumberAs};
217///
218/// fn clamp_any<Number, Limit>(x: Number, min: Limit, max: Limit) -> Number
219/// where
220///     Number: PrimitiveNumber + PrimitiveNumberAs<Limit>,
221///     Limit: PartialOrd,
222/// {
223///     assert!(min <= max);
224///     let y = x.as_to::<Limit>();
225///     if y <= min {
226///         Number::as_from(min)
227///     } else if y >= max {
228///         Number::as_from(max)
229///     } else {
230///         x
231///     }
232/// }
233///
234/// assert_eq!(clamp_any(1.23, 0_i8, 10_i8), 1.23);
235/// assert_eq!(clamp_any(1.23, -1_i8, 1_i8), 1.0);
236/// assert_eq!(clamp_any(i128::MAX, 0.0, 1e100), i128::MAX);
237/// ```
238pub trait PrimitiveNumberAs<T> {
239    #[doc(hidden)]
240    #[expect(private_interfaces)]
241    fn __as_from(x: T, _: SealedToken) -> Self;
242
243    #[doc(hidden)]
244    #[expect(private_interfaces)]
245    fn __as_to(x: Self, _: SealedToken) -> T;
246}
247
248macro_rules! impl_primitive {
249    ($($Number:ident),+) => {$(
250        impl Sealed for $Number {}
251        impl Sealed for &$Number {}
252
253        impl PrimitiveNumber for $Number {
254            type Bytes = [u8; size_of::<Self>()];
255
256            forward! {
257                fn from_be_bytes(bytes: Self::Bytes) -> Self;
258                fn from_le_bytes(bytes: Self::Bytes) -> Self;
259                fn from_ne_bytes(bytes: Self::Bytes) -> Self;
260            }
261            forward! {
262                fn midpoint(self, other: Self) -> Self;
263                fn to_be_bytes(self) -> Self::Bytes;
264                fn to_le_bytes(self) -> Self::Bytes;
265                fn to_ne_bytes(self) -> Self::Bytes;
266            }
267        }
268
269        impl PrimitiveNumberRef<$Number> for &$Number {}
270
271        impl_primitive!($Number as f32, f64);
272        impl_primitive!($Number as i8, i16, i32, i64, i128, isize);
273        impl_primitive!($Number as u8, u16, u32, u64, u128, usize);
274    )+};
275
276    ($Number:ident as $($Other:ident),+) => {$(
277        impl PrimitiveNumberAs<$Other> for $Number {
278            #[inline]
279            #[expect(private_interfaces)]
280            fn __as_from(x: $Other, _: SealedToken) -> Self {
281                x as Self
282            }
283
284            #[inline]
285            #[expect(private_interfaces)]
286            fn __as_to(x: Self, _: SealedToken) -> $Other {
287                x as $Other
288            }
289        }
290    )+}
291}
292
293impl_primitive!(f32, f64);
294impl_primitive!(i8, i16, i32, i64, i128, isize);
295impl_primitive!(u8, u16, u32, u64, u128, usize);
num_primitive/number.rs

num_primitive/
number.rs
