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Constify cmp_min_max_by. #102245

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Sep 25, 2022
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Constify cmp_min_max_by. #102245

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55 changes: 49 additions & 6 deletions library/core/src/cmp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@

#![stable(feature = "rust1", since = "1.0.0")]

use crate::const_closure::ConstFnMutClosure;
use crate::marker::Destruct;
use crate::marker::StructuralPartialEq;

Expand Down Expand Up @@ -1222,7 +1223,12 @@ pub const fn min<T: ~const Ord + ~const Destruct>(v1: T, v2: T) -> T {
#[inline]
#[must_use]
#[stable(feature = "cmp_min_max_by", since = "1.53.0")]
pub fn min_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
#[rustc_const_unstable(feature = "const_cmp", issue = "92391")]
pub const fn min_by<T, F: ~const FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T
where
T: ~const Destruct,
F: ~const Destruct,
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I don't think F needs to be dropped here.

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Ohh right thats an FnOnce, will fix

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I am fixing this in the const iterator PR.

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Ok thanks!

{
match compare(&v1, &v2) {
Ordering::Less | Ordering::Equal => v1,
Ordering::Greater => v2,
Expand All @@ -1244,8 +1250,24 @@ pub fn min_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
#[inline]
#[must_use]
#[stable(feature = "cmp_min_max_by", since = "1.53.0")]
pub fn min_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T {
min_by(v1, v2, |v1, v2| f(v1).cmp(&f(v2)))
#[rustc_const_unstable(feature = "const_cmp", issue = "92391")]
pub const fn min_by_key<T, F: ~const FnMut(&T) -> K, K: ~const Ord>(v1: T, v2: T, mut f: F) -> T
where
T: ~const Destruct,
F: ~const Destruct,
K: ~const Destruct,
{
const fn imp<T, F: ~const FnMut(&T) -> K, K: ~const Ord>(
f: &mut F,
(v1, v2): (&T, &T),
) -> Ordering
where
T: ~const Destruct,
K: ~const Destruct,
{
f(v1).cmp(&f(v2))
}
min_by(v1, v2, ConstFnMutClosure::new(&mut f, imp))
}

/// Compares and returns the maximum of two values.
Expand Down Expand Up @@ -1286,7 +1308,12 @@ pub const fn max<T: ~const Ord + ~const Destruct>(v1: T, v2: T) -> T {
#[inline]
#[must_use]
#[stable(feature = "cmp_min_max_by", since = "1.53.0")]
pub fn max_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
#[rustc_const_unstable(feature = "const_cmp", issue = "92391")]
pub const fn max_by<T, F: ~const FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T
where
T: ~const Destruct,
F: ~const Destruct,
{
match compare(&v1, &v2) {
Ordering::Less | Ordering::Equal => v2,
Ordering::Greater => v1,
Expand All @@ -1308,8 +1335,24 @@ pub fn max_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
#[inline]
#[must_use]
#[stable(feature = "cmp_min_max_by", since = "1.53.0")]
pub fn max_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T {
max_by(v1, v2, |v1, v2| f(v1).cmp(&f(v2)))
#[rustc_const_unstable(feature = "const_cmp", issue = "92391")]
pub const fn max_by_key<T, F: ~const FnMut(&T) -> K, K: ~const Ord>(v1: T, v2: T, mut f: F) -> T
where
T: ~const Destruct,
F: ~const Destruct,
K: ~const Destruct,
{
const fn imp<T, F: ~const FnMut(&T) -> K, K: ~const Ord>(
f: &mut F,
(v1, v2): (&T, &T),
) -> Ordering
where
T: ~const Destruct,
K: ~const Destruct,
{
f(v1).cmp(&f(v2))
}
max_by(v1, v2, ConstFnMutClosure::new(&mut f, imp))
}

// Implementation of PartialEq, Eq, PartialOrd and Ord for primitive types
Expand Down