diff options
| -rw-r--r-- | library/core/src/num/int_macros.rs | 78 | ||||
| -rw-r--r-- | library/core/tests/lib.rs | 1 | ||||
| -rw-r--r-- | library/core/tests/num/int_macros.rs | 26 | ||||
| -rw-r--r-- | library/core/tests/num/uint_macros.rs | 22 |
4 files changed, 127 insertions, 0 deletions
diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs index 92b12ed3352..e7deb728d15 100644 --- a/library/core/src/num/int_macros.rs +++ b/library/core/src/num/int_macros.rs @@ -1518,6 +1518,51 @@ macro_rules! int_impl { (a as Self, b) } + /// Calculates `self + rhs + carry` without the ability to overflow. + /// + /// Performs "signed ternary addition" which takes in an extra bit to add, and may return an + /// additional bit of overflow. This signed function is used only on the highest-ordered data, + /// for which the signed overflow result indicates whether the big integer overflowed or not. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// #![feature(bigint_helper_methods)] + #[doc = concat!("assert_eq!(5", stringify!($SelfT), ".carrying_add(2, false), (7, false));")] + #[doc = concat!("assert_eq!(5", stringify!($SelfT), ".carrying_add(2, true), (8, false));")] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MAX.carrying_add(1, false), (", stringify!($SelfT), "::MIN, true));")] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MAX.carrying_add(0, true), (", stringify!($SelfT), "::MIN, true));")] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MAX.carrying_add(1, true), (", stringify!($SelfT), "::MIN + 1, true));")] + #[doc = concat!("assert_eq!(", + stringify!($SelfT), "::MAX.carrying_add(", stringify!($SelfT), "::MAX, true), ", + "(-1, true));" + )] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MIN.carrying_add(-1, true), (", stringify!($SelfT), "::MIN, false));")] + #[doc = concat!("assert_eq!(0", stringify!($SelfT), ".carrying_add(", stringify!($SelfT), "::MAX, true), (", stringify!($SelfT), "::MIN, true));")] + /// ``` + /// + /// If `carry` is false, this method is equivalent to [`overflowing_add`](Self::overflowing_add): + /// + /// ``` + /// #![feature(bigint_helper_methods)] + #[doc = concat!("assert_eq!(5_", stringify!($SelfT), ".carrying_add(2, false), 5_", stringify!($SelfT), ".overflowing_add(2));")] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MAX.carrying_add(1, false), ", stringify!($SelfT), "::MAX.overflowing_add(1));")] + /// ``` + #[unstable(feature = "bigint_helper_methods", issue = "85532")] + #[rustc_const_unstable(feature = "const_bigint_helper_methods", issue = "85532")] + #[must_use = "this returns the result of the operation, \ + without modifying the original"] + #[inline] + pub const fn carrying_add(self, rhs: Self, carry: bool) -> (Self, bool) { + // note: longer-term this should be done via an intrinsic. + // note: no intermediate overflow is required (https://github.com/rust-lang/rust/issues/85532#issuecomment-1032214946). + let (a, b) = self.overflowing_add(rhs); + let (c, d) = a.overflowing_add(carry as $SelfT); + (c, b != d) + } + /// Calculates `self` + `rhs` with an unsigned `rhs` /// /// Returns a tuple of the addition along with a boolean indicating @@ -1569,6 +1614,39 @@ macro_rules! int_impl { (a as Self, b) } + /// Calculates `self - rhs - borrow` without the ability to overflow. + /// + /// Performs "signed ternary subtraction" which takes in an extra bit to subtract, and may return an + /// additional bit of overflow. This signed function is used only on the highest-ordered data, + /// for which the signed overflow result indicates whether the big integer overflowed or not. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// #![feature(bigint_helper_methods)] + #[doc = concat!("assert_eq!(5", stringify!($SelfT), ".borrowing_sub(2, false), (3, false));")] + #[doc = concat!("assert_eq!(5", stringify!($SelfT), ".borrowing_sub(2, true), (2, false));")] + #[doc = concat!("assert_eq!(0", stringify!($SelfT), ".borrowing_sub(1, false), (-1, false));")] + #[doc = concat!("assert_eq!(0", stringify!($SelfT), ".borrowing_sub(1, true), (-2, false));")] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MIN.borrowing_sub(1, true), (", stringify!($SelfT), "::MAX - 1, true));")] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MAX.borrowing_sub(-1, false), (", stringify!($SelfT), "::MIN, true));")] + #[doc = concat!("assert_eq!(", stringify!($SelfT), "::MAX.borrowing_sub(-1, true), (", stringify!($SelfT), "::MAX, false));")] + /// ``` + #[unstable(feature = "bigint_helper_methods", issue = "85532")] + #[rustc_const_unstable(feature = "const_bigint_helper_methods", issue = "85532")] + #[must_use = "this returns the result of the operation, \ + without modifying the original"] + #[inline] + pub const fn borrowing_sub(self, rhs: Self, borrow: bool) -> (Self, bool) { + // note: longer-term this should be done via an intrinsic. + // note: no intermediate overflow is required (https://github.com/rust-lang/rust/issues/85532#issuecomment-1032214946). + let (a, b) = self.overflowing_sub(rhs); + let (c, d) = a.overflowing_sub(borrow as $SelfT); + (c, b != d) + } + /// Calculates `self` - `rhs` with an unsigned `rhs` /// /// Returns a tuple of the subtraction along with a boolean indicating diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs index c315f3a7975..4a0e162bc4a 100644 --- a/library/core/tests/lib.rs +++ b/library/core/tests/lib.rs @@ -3,6 +3,7 @@ #![feature(array_methods)] #![feature(array_windows)] #![feature(bench_black_box)] +#![feature(bigint_helper_methods)] #![feature(cell_update)] #![feature(const_assume)] #![feature(const_black_box)] diff --git a/library/core/tests/num/int_macros.rs b/library/core/tests/num/int_macros.rs index 8b84a78e6be..18c55e43aac 100644 --- a/library/core/tests/num/int_macros.rs +++ b/library/core/tests/num/int_macros.rs @@ -338,6 +338,32 @@ macro_rules! int_module { assert_eq!(MIN.checked_next_multiple_of(-3), None); assert_eq!(MIN.checked_next_multiple_of(-1), Some(MIN)); } + + #[test] + fn test_carrying_add() { + assert_eq!($T::MAX.carrying_add(1, false), ($T::MIN, true)); + assert_eq!($T::MAX.carrying_add(0, true), ($T::MIN, true)); + assert_eq!($T::MAX.carrying_add(1, true), ($T::MIN + 1, true)); + assert_eq!($T::MAX.carrying_add(-1, false), ($T::MAX - 1, false)); + assert_eq!($T::MAX.carrying_add(-1, true), ($T::MAX, false)); // no intermediate overflow + assert_eq!($T::MIN.carrying_add(-1, false), ($T::MAX, true)); + assert_eq!($T::MIN.carrying_add(-1, true), ($T::MIN, false)); // no intermediate overflow + assert_eq!((0 as $T).carrying_add($T::MAX, true), ($T::MIN, true)); + assert_eq!((0 as $T).carrying_add($T::MIN, true), ($T::MIN + 1, false)); + } + + #[test] + fn test_borrowing_sub() { + assert_eq!($T::MIN.borrowing_sub(1, false), ($T::MAX, true)); + assert_eq!($T::MIN.borrowing_sub(0, true), ($T::MAX, true)); + assert_eq!($T::MIN.borrowing_sub(1, true), ($T::MAX - 1, true)); + assert_eq!($T::MIN.borrowing_sub(-1, false), ($T::MIN + 1, false)); + assert_eq!($T::MIN.borrowing_sub(-1, true), ($T::MIN, false)); // no intermediate overflow + assert_eq!($T::MAX.borrowing_sub(-1, false), ($T::MIN, true)); + assert_eq!($T::MAX.borrowing_sub(-1, true), ($T::MAX, false)); // no intermediate overflow + assert_eq!((0 as $T).borrowing_sub($T::MIN, false), ($T::MIN, true)); + assert_eq!((0 as $T).borrowing_sub($T::MIN, true), ($T::MAX, false)); + } } }; } diff --git a/library/core/tests/num/uint_macros.rs b/library/core/tests/num/uint_macros.rs index 93ae620c233..15ae9f2324f 100644 --- a/library/core/tests/num/uint_macros.rs +++ b/library/core/tests/num/uint_macros.rs @@ -230,6 +230,28 @@ macro_rules! uint_module { assert_eq!((1 as $T).checked_next_multiple_of(0), None); assert_eq!(MAX.checked_next_multiple_of(2), None); } + + #[test] + fn test_carrying_add() { + assert_eq!($T::MAX.carrying_add(1, false), (0, true)); + assert_eq!($T::MAX.carrying_add(0, true), (0, true)); + assert_eq!($T::MAX.carrying_add(1, true), (1, true)); + + assert_eq!($T::MIN.carrying_add($T::MAX, false), ($T::MAX, false)); + assert_eq!($T::MIN.carrying_add(0, true), (1, false)); + assert_eq!($T::MIN.carrying_add($T::MAX, true), (0, true)); + } + + #[test] + fn test_borrowing_sub() { + assert_eq!($T::MIN.borrowing_sub(1, false), ($T::MAX, true)); + assert_eq!($T::MIN.borrowing_sub(0, true), ($T::MAX, true)); + assert_eq!($T::MIN.borrowing_sub(1, true), ($T::MAX - 1, true)); + + assert_eq!($T::MAX.borrowing_sub($T::MAX, false), (0, false)); + assert_eq!($T::MAX.borrowing_sub(0, true), ($T::MAX - 1, false)); + assert_eq!($T::MAX.borrowing_sub($T::MAX, true), ($T::MAX, true)); + } } }; } |