diff options
Diffstat (limited to 'library/core/src/num/mod.rs')
| -rw-r--r-- | library/core/src/num/mod.rs | 135 |
1 files changed, 0 insertions, 135 deletions
diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs index 357a85ae843..1f5b8ce6c6e 100644 --- a/library/core/src/num/mod.rs +++ b/library/core/src/num/mod.rs @@ -228,134 +228,6 @@ macro_rules! midpoint_impl { }; } -macro_rules! widening_impl { - ($SelfT:ty, $WideT:ty, $BITS:literal, unsigned) => { - /// Calculates the complete product `self * rhs` without the possibility to overflow. - /// - /// This returns the low-order (wrapping) bits and the high-order (overflow) bits - /// of the result as two separate values, in that order. - /// - /// If you also need to add a carry to the wide result, then you want - /// [`Self::carrying_mul`] instead. - /// - /// # Examples - /// - /// Basic usage: - /// - /// Please note that this example is shared between integer types. - /// Which explains why `u32` is used here. - /// - /// ``` - /// #![feature(bigint_helper_methods)] - /// assert_eq!(5u32.widening_mul(2), (10, 0)); - /// assert_eq!(1_000_000_000u32.widening_mul(10), (1410065408, 2)); - /// ``` - #[unstable(feature = "bigint_helper_methods", issue = "85532")] - #[must_use = "this returns the result of the operation, \ - without modifying the original"] - #[inline] - pub const fn widening_mul(self, rhs: Self) -> (Self, Self) { - // note: longer-term this should be done via an intrinsic, - // but for now we can deal without an impl for u128/i128 - // SAFETY: overflow will be contained within the wider types - let wide = unsafe { (self as $WideT).unchecked_mul(rhs as $WideT) }; - (wide as $SelfT, (wide >> $BITS) as $SelfT) - } - - /// Calculates the "full multiplication" `self * rhs + carry` - /// without the possibility to overflow. - /// - /// This returns the low-order (wrapping) bits and the high-order (overflow) bits - /// of the result as two separate values, in that order. - /// - /// Performs "long multiplication" which takes in an extra amount to add, and may return an - /// additional amount of overflow. This allows for chaining together multiple - /// multiplications to create "big integers" which represent larger values. - /// - /// If you don't need the `carry`, then you can use [`Self::widening_mul`] instead. - /// - /// # Examples - /// - /// Basic usage: - /// - /// Please note that this example is shared between integer types. - /// Which explains why `u32` is used here. - /// - /// ``` - /// #![feature(bigint_helper_methods)] - /// assert_eq!(5u32.carrying_mul(2, 0), (10, 0)); - /// assert_eq!(5u32.carrying_mul(2, 10), (20, 0)); - /// assert_eq!(1_000_000_000u32.carrying_mul(10, 0), (1410065408, 2)); - /// assert_eq!(1_000_000_000u32.carrying_mul(10, 10), (1410065418, 2)); - #[doc = concat!("assert_eq!(", - stringify!($SelfT), "::MAX.carrying_mul(", stringify!($SelfT), "::MAX, ", stringify!($SelfT), "::MAX), ", - "(0, ", stringify!($SelfT), "::MAX));" - )] - /// ``` - /// - /// This is the core operation needed for scalar multiplication when - /// implementing it for wider-than-native types. - /// - /// ``` - /// #![feature(bigint_helper_methods)] - /// fn scalar_mul_eq(little_endian_digits: &mut Vec<u16>, multiplicand: u16) { - /// let mut carry = 0; - /// for d in little_endian_digits.iter_mut() { - /// (*d, carry) = d.carrying_mul(multiplicand, carry); - /// } - /// if carry != 0 { - /// little_endian_digits.push(carry); - /// } - /// } - /// - /// let mut v = vec![10, 20]; - /// scalar_mul_eq(&mut v, 3); - /// assert_eq!(v, [30, 60]); - /// - /// assert_eq!(0x87654321_u64 * 0xFEED, 0x86D3D159E38D); - /// let mut v = vec![0x4321, 0x8765]; - /// scalar_mul_eq(&mut v, 0xFEED); - /// assert_eq!(v, [0xE38D, 0xD159, 0x86D3]); - /// ``` - /// - /// If `carry` is zero, this is similar to [`overflowing_mul`](Self::overflowing_mul), - /// except that it gives the value of the overflow instead of just whether one happened: - /// - /// ``` - /// #![feature(bigint_helper_methods)] - /// let r = u8::carrying_mul(7, 13, 0); - /// assert_eq!((r.0, r.1 != 0), u8::overflowing_mul(7, 13)); - /// let r = u8::carrying_mul(13, 42, 0); - /// assert_eq!((r.0, r.1 != 0), u8::overflowing_mul(13, 42)); - /// ``` - /// - /// The value of the first field in the returned tuple matches what you'd get - /// by combining the [`wrapping_mul`](Self::wrapping_mul) and - /// [`wrapping_add`](Self::wrapping_add) methods: - /// - /// ``` - /// #![feature(bigint_helper_methods)] - /// assert_eq!( - /// 789_u16.carrying_mul(456, 123).0, - /// 789_u16.wrapping_mul(456).wrapping_add(123), - /// ); - /// ``` - #[unstable(feature = "bigint_helper_methods", issue = "85532")] - #[must_use = "this returns the result of the operation, \ - without modifying the original"] - #[inline] - pub const fn carrying_mul(self, rhs: Self, carry: Self) -> (Self, Self) { - // note: longer-term this should be done via an intrinsic, - // but for now we can deal without an impl for u128/i128 - // SAFETY: overflow will be contained within the wider types - let wide = unsafe { - (self as $WideT).unchecked_mul(rhs as $WideT).unchecked_add(carry as $WideT) - }; - (wide as $SelfT, (wide >> $BITS) as $SelfT) - } - }; -} - impl i8 { int_impl! { Self = i8, @@ -576,7 +448,6 @@ impl u8 { from_xe_bytes_doc = u8_xe_bytes_doc!(), bound_condition = "", } - widening_impl! { u8, u16, 8, unsigned } midpoint_impl! { u8, u16, unsigned } /// Checks if the value is within the ASCII range. @@ -1192,7 +1063,6 @@ impl u16 { from_xe_bytes_doc = "", bound_condition = "", } - widening_impl! { u16, u32, 16, unsigned } midpoint_impl! { u16, u32, unsigned } /// Checks if the value is a Unicode surrogate code point, which are disallowed values for [`char`]. @@ -1240,7 +1110,6 @@ impl u32 { from_xe_bytes_doc = "", bound_condition = "", } - widening_impl! { u32, u64, 32, unsigned } midpoint_impl! { u32, u64, unsigned } } @@ -1264,7 +1133,6 @@ impl u64 { from_xe_bytes_doc = "", bound_condition = "", } - widening_impl! { u64, u128, 64, unsigned } midpoint_impl! { u64, u128, unsigned } } @@ -1314,7 +1182,6 @@ impl usize { from_xe_bytes_doc = usize_isize_from_xe_bytes_doc!(), bound_condition = " on 16-bit targets", } - widening_impl! { usize, u32, 16, unsigned } midpoint_impl! { usize, u32, unsigned } } @@ -1339,7 +1206,6 @@ impl usize { from_xe_bytes_doc = usize_isize_from_xe_bytes_doc!(), bound_condition = " on 32-bit targets", } - widening_impl! { usize, u64, 32, unsigned } midpoint_impl! { usize, u64, unsigned } } @@ -1364,7 +1230,6 @@ impl usize { from_xe_bytes_doc = usize_isize_from_xe_bytes_doc!(), bound_condition = " on 64-bit targets", } - widening_impl! { usize, u128, 64, unsigned } midpoint_impl! { usize, u128, unsigned } } |