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Richard Smith b8814f6c80 Add named constraints for Eq and Ordered. (#7714)
Also add a default for `EqWith.NotEqual`.

Switch advent examples to use these named constraints, and also go
through all the other TODOs in the advent examples and fix the ones that
are trivially fixable now.
2026-09-03 16:20:13 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
library "sort";
fn Swap[T: Core.Copy & Core.Destroy](ref from: T, ref to: T) {
var tmp: T = from;
from = to;
to = tmp;
}
fn Partition
[T: Core.Copy & Core.Destroy & Core.Ordered, N: Core.IntLiteral]
(ref a: array(T, N), from_in: i32, to_in: i32) -> i32 {
var pivot_index: i32 = from_in;
let pivot: T = a[pivot_index];
var from: i32 = from_in + 1;
var to: i32 = to_in;
while (from < to) {
if (a[from] <= pivot) {
++from;
} else if (a[to - 1] > pivot) {
--to;
} else {
// Element at `from` is > pivot, and
// element at `to - 1` is <= pivot.
Swap(ref a[from], ref a[to - 1]);
++from;
--to;
}
}
Swap(ref a[pivot_index], ref a[from - 1]);
return from - 1;
}
fn Quicksort
[T: Core.Copy & Core.Destroy & Core.Ordered, N: Core.IntLiteral]
(ref a: array(T, N), from: i32, to: i32) {
if (from + 1 >= to) { return; }
var pivot: i32 = Partition(ref a, from, to);
Quicksort(ref a, from, pivot);
Quicksort(ref a, pivot + 1, to);
}