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Rollup merge of #90848 - scottmcm:remove-signed-bigint-helpers, r=jos…
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…htriplett

Remove bigint_helper_methods for *signed* types

This PR inspired by `@cuviper's` comment @ #90541 (comment)

These are working well for *unsigned* types, so keep those, but for the the *signed* ones there are a bunch of questions about what the semantics and API should be.  For the main "helpers for big integer implementations" use, there's no need for the signed versions anyway.  There are plenty of other methods which exist for unsigned types but not signed ones, like `next_power_of_two`, so this isn't unusual.

Fixes #90541
Tracking issue #85532
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@JohnTitor
JohnTitor authored Nov 16, 2021
2 parents 12d5297 + 6323f92 commit fb96ecc
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54 changes: 0 additions & 54 deletions library/core/src/num/int_macros.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1511,33 +1511,6 @@ macro_rules! int_impl {
(a as Self, b)
}

/// Calculates `self + rhs + carry` without the ability to overflow.
///
/// Performs "ternary addition" which takes in an extra bit to add, and may return an
/// additional bit of overflow. This allows for chaining together multiple additions
/// to create "big integers" which represent larger values.
///
/// # 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, false));")]
#[doc = concat!("assert_eq!(", stringify!($SelfT), "::MAX.carrying_add(1, true), (", stringify!($SelfT), "::MIN + 1, 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 carrying_add(self, rhs: Self, carry: bool) -> (Self, bool) {
let (sum, carry) = (self as $UnsignedT).carrying_add(rhs as $UnsignedT, carry);
(sum as $SelfT, carry)
}

/// Calculates `self` + `rhs` with an unsigned `rhs`
///
/// Returns a tuple of the addition along with a boolean indicating
Expand Down Expand Up @@ -1589,33 +1562,6 @@ macro_rules! int_impl {
(a as Self, b)
}

/// Calculates `self - rhs - borrow` without the ability to overflow.
///
/// Performs "ternary subtraction" which takes in an extra bit to subtract, and may return
/// an additional bit of overflow. This allows for chaining together multiple subtractions
/// to create "big integers" which represent larger values.
///
/// # 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!(", stringify!($SelfT), "::MIN.borrowing_sub(1, false), (", stringify!($SelfT), "::MAX, false));")]
#[doc = concat!("assert_eq!(", stringify!($SelfT), "::MIN.borrowing_sub(1, true), (", stringify!($SelfT), "::MAX - 1, 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) {
let (sum, borrow) = (self as $UnsignedT).borrowing_sub(rhs as $UnsignedT, borrow);
(sum as $SelfT, borrow)
}

/// Calculates `self` - `rhs` with an unsigned `rhs`
///
/// Returns a tuple of the subtraction along with a boolean indicating
Expand Down
15 changes: 1 addition & 14 deletions library/core/src/num/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -95,12 +95,6 @@ depending on the target pointer size.

macro_rules! widening_impl {
($SelfT:ty, $WideT:ty, $BITS:literal, unsigned) => {
widening_impl!($SelfT, $WideT, $BITS, "");
};
($SelfT:ty, $WideT:ty, $BITS:literal, signed) => {
widening_impl!($SelfT, $WideT, $BITS, "# //");
};
($SelfT:ty, $WideT:ty, $BITS:literal, $AdaptiveTestPrefix:literal) => {
/// Calculates the complete product `self * rhs` without the possibility to overflow.
///
/// This returns the low-order (wrapping) bits and the high-order (overflow) bits
Expand Down Expand Up @@ -154,7 +148,7 @@ macro_rules! widening_impl {
/// assert_eq!(5u32.carrying_mul(2, 10), (20, 0));
/// assert_eq!(1_000_000_000u32.carrying_mul(10, 0), (1410065408, 2));
/// assert_eq!(1_000_000_000u32.carrying_mul(10, 10), (1410065418, 2));
#[doc = concat!($AdaptiveTestPrefix, "assert_eq!(",
#[doc = concat!("assert_eq!(",
stringify!($SelfT), "::MAX.carrying_mul(", stringify!($SelfT), "::MAX, ", stringify!($SelfT), "::MAX), ",
"(0, ", stringify!($SelfT), "::MAX));"
)]
Expand Down Expand Up @@ -203,22 +197,19 @@ macro_rules! widening_impl {
impl i8 {
int_impl! { i8, i8, u8, 8, 7, -128, 127, 2, "-0x7e", "0xa", "0x12", "0x12", "0x48",
"[0x12]", "[0x12]", "", "" }
widening_impl! { i8, i16, 8, signed }
}

#[lang = "i16"]
impl i16 {
int_impl! { i16, i16, u16, 16, 15, -32768, 32767, 4, "-0x5ffd", "0x3a", "0x1234", "0x3412",
"0x2c48", "[0x34, 0x12]", "[0x12, 0x34]", "", "" }
widening_impl! { i16, i32, 16, signed }
}

#[lang = "i32"]
impl i32 {
int_impl! { i32, i32, u32, 32, 31, -2147483648, 2147483647, 8, "0x10000b3", "0xb301",
"0x12345678", "0x78563412", "0x1e6a2c48", "[0x78, 0x56, 0x34, 0x12]",
"[0x12, 0x34, 0x56, 0x78]", "", "" }
widening_impl! { i32, i64, 32, signed }
}

#[lang = "i64"]
Expand All @@ -227,7 +218,6 @@ impl i64 {
"0xaa00000000006e1", "0x6e10aa", "0x1234567890123456", "0x5634129078563412",
"0x6a2c48091e6a2c48", "[0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]",
"[0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]", "", "" }
widening_impl! { i64, i128, 64, signed }
}

#[lang = "i128"]
Expand All @@ -248,7 +238,6 @@ impl isize {
int_impl! { isize, i16, usize, 16, 15, -32768, 32767, 4, "-0x5ffd", "0x3a", "0x1234",
"0x3412", "0x2c48", "[0x34, 0x12]", "[0x12, 0x34]",
usize_isize_to_xe_bytes_doc!(), usize_isize_from_xe_bytes_doc!() }
widening_impl! { isize, i32, 16, signed }
}

#[cfg(target_pointer_width = "32")]
Expand All @@ -258,7 +247,6 @@ impl isize {
"0x12345678", "0x78563412", "0x1e6a2c48", "[0x78, 0x56, 0x34, 0x12]",
"[0x12, 0x34, 0x56, 0x78]",
usize_isize_to_xe_bytes_doc!(), usize_isize_from_xe_bytes_doc!() }
widening_impl! { isize, i64, 32, signed }
}

#[cfg(target_pointer_width = "64")]
Expand All @@ -269,7 +257,6 @@ impl isize {
"0x6a2c48091e6a2c48", "[0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]",
"[0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]",
usize_isize_to_xe_bytes_doc!(), usize_isize_from_xe_bytes_doc!() }
widening_impl! { isize, i128, 64, signed }
}

/// If 6th bit set ascii is upper case.
Expand Down

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