num_traits/ops/
saturating.rs

1use core::ops::{Add, Mul, Sub};
2
3/// Saturating math operations. Deprecated, use `SaturatingAdd`, `SaturatingSub` and
4/// `SaturatingMul` instead.
5pub trait Saturating {
6    /// Saturating addition operator.
7    /// Returns a+b, saturating at the numeric bounds instead of overflowing.
8    fn saturating_add(self, v: Self) -> Self;
9
10    /// Saturating subtraction operator.
11    /// Returns a-b, saturating at the numeric bounds instead of overflowing.
12    fn saturating_sub(self, v: Self) -> Self;
13}
14
15macro_rules! deprecated_saturating_impl {
16    ($trait_name:ident for $($t:ty)*) => {$(
17        impl $trait_name for $t {
18            #[inline]
19            fn saturating_add(self, v: Self) -> Self {
20                Self::saturating_add(self, v)
21            }
22
23            #[inline]
24            fn saturating_sub(self, v: Self) -> Self {
25                Self::saturating_sub(self, v)
26            }
27        }
28    )*}
29}
30
31deprecated_saturating_impl!(Saturating for isize i8 i16 i32 i64 i128);
32deprecated_saturating_impl!(Saturating for usize u8 u16 u32 u64 u128);
33
34macro_rules! saturating_impl {
35    ($trait_name:ident, $method:ident, $t:ty) => {
36        impl $trait_name for $t {
37            #[inline]
38            fn $method(&self, v: &Self) -> Self {
39                <$t>::$method(*self, *v)
40            }
41        }
42    };
43}
44
45/// Performs addition that saturates at the numeric bounds instead of overflowing.
46pub trait SaturatingAdd: Sized + Add<Self, Output = Self> {
47    /// Saturating addition. Computes `self + other`, saturating at the relevant high or low boundary of
48    /// the type.
49    fn saturating_add(&self, v: &Self) -> Self;
50}
51
52saturating_impl!(SaturatingAdd, saturating_add, u8);
53saturating_impl!(SaturatingAdd, saturating_add, u16);
54saturating_impl!(SaturatingAdd, saturating_add, u32);
55saturating_impl!(SaturatingAdd, saturating_add, u64);
56saturating_impl!(SaturatingAdd, saturating_add, usize);
57saturating_impl!(SaturatingAdd, saturating_add, u128);
58
59saturating_impl!(SaturatingAdd, saturating_add, i8);
60saturating_impl!(SaturatingAdd, saturating_add, i16);
61saturating_impl!(SaturatingAdd, saturating_add, i32);
62saturating_impl!(SaturatingAdd, saturating_add, i64);
63saturating_impl!(SaturatingAdd, saturating_add, isize);
64saturating_impl!(SaturatingAdd, saturating_add, i128);
65
66/// Performs subtraction that saturates at the numeric bounds instead of overflowing.
67pub trait SaturatingSub: Sized + Sub<Self, Output = Self> {
68    /// Saturating subtraction. Computes `self - other`, saturating at the relevant high or low boundary of
69    /// the type.
70    fn saturating_sub(&self, v: &Self) -> Self;
71}
72
73saturating_impl!(SaturatingSub, saturating_sub, u8);
74saturating_impl!(SaturatingSub, saturating_sub, u16);
75saturating_impl!(SaturatingSub, saturating_sub, u32);
76saturating_impl!(SaturatingSub, saturating_sub, u64);
77saturating_impl!(SaturatingSub, saturating_sub, usize);
78saturating_impl!(SaturatingSub, saturating_sub, u128);
79
80saturating_impl!(SaturatingSub, saturating_sub, i8);
81saturating_impl!(SaturatingSub, saturating_sub, i16);
82saturating_impl!(SaturatingSub, saturating_sub, i32);
83saturating_impl!(SaturatingSub, saturating_sub, i64);
84saturating_impl!(SaturatingSub, saturating_sub, isize);
85saturating_impl!(SaturatingSub, saturating_sub, i128);
86
87/// Performs multiplication that saturates at the numeric bounds instead of overflowing.
88pub trait SaturatingMul: Sized + Mul<Self, Output = Self> {
89    /// Saturating multiplication. Computes `self * other`, saturating at the relevant high or low boundary of
90    /// the type.
91    fn saturating_mul(&self, v: &Self) -> Self;
92}
93
94saturating_impl!(SaturatingMul, saturating_mul, u8);
95saturating_impl!(SaturatingMul, saturating_mul, u16);
96saturating_impl!(SaturatingMul, saturating_mul, u32);
97saturating_impl!(SaturatingMul, saturating_mul, u64);
98saturating_impl!(SaturatingMul, saturating_mul, usize);
99saturating_impl!(SaturatingMul, saturating_mul, u128);
100
101saturating_impl!(SaturatingMul, saturating_mul, i8);
102saturating_impl!(SaturatingMul, saturating_mul, i16);
103saturating_impl!(SaturatingMul, saturating_mul, i32);
104saturating_impl!(SaturatingMul, saturating_mul, i64);
105saturating_impl!(SaturatingMul, saturating_mul, isize);
106saturating_impl!(SaturatingMul, saturating_mul, i128);
107
108// TODO: add SaturatingNeg for signed integer primitives once the saturating_neg() API is stable.
109
110#[test]
111fn test_saturating_traits() {
112    fn saturating_add<T: SaturatingAdd>(a: T, b: T) -> T {
113        a.saturating_add(&b)
114    }
115    fn saturating_sub<T: SaturatingSub>(a: T, b: T) -> T {
116        a.saturating_sub(&b)
117    }
118    fn saturating_mul<T: SaturatingMul>(a: T, b: T) -> T {
119        a.saturating_mul(&b)
120    }
121    assert_eq!(saturating_add(255, 1), 255u8);
122    assert_eq!(saturating_add(127, 1), 127i8);
123    assert_eq!(saturating_add(-128, -1), -128i8);
124    assert_eq!(saturating_sub(0, 1), 0u8);
125    assert_eq!(saturating_sub(-128, 1), -128i8);
126    assert_eq!(saturating_sub(127, -1), 127i8);
127    assert_eq!(saturating_mul(255, 2), 255u8);
128    assert_eq!(saturating_mul(127, 2), 127i8);
129    assert_eq!(saturating_mul(-128, 2), -128i8);
130}
num_traits/ops/saturating.rs

num_traits/ops/
saturating.rs
