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52212f4323
slices.SortFunc suffered a late-in-cycle API breakage. Updates #cleanup Signed-off-by: David Anderson <danderson@tailscale.com>
60 lines
1.4 KiB
Go
60 lines
1.4 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package cmpx has code that will likely land in a future version of Go, but
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// we want sooner.
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package cmpx
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// Or returns the first non-zero element of list, or else returns the zero T.
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//
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// This is the proposal from
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// https://github.com/golang/go/issues/60204#issuecomment-1581245334.
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func Or[T comparable](list ...T) T {
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// TODO(bradfitz): remove the comparable constraint so we can use this
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// with funcs too and use reflect to see whether they're non-zero? 🤷♂️
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var zero T
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for _, v := range list {
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if v != zero {
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return v
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}
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}
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return zero
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}
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// Ordered is cmp.Ordered from Go 1.21.
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type Ordered interface {
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~int | ~int8 | ~int16 | ~int32 | ~int64 |
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~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
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~float32 | ~float64 |
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~string
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}
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// Compare returns
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//
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// -1 if x is less than y,
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// 0 if x equals y,
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// +1 if x is greater than y.
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//
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// For floating-point types, a NaN is considered less than any non-NaN,
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// a NaN is considered equal to a NaN, and -0.0 is equal to 0.0.
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func Compare[T Ordered](x, y T) int {
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xNaN := isNaN(x)
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yNaN := isNaN(y)
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if xNaN && yNaN {
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return 0
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}
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if xNaN || x < y {
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return -1
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}
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if yNaN || x > y {
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return +1
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}
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return 0
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}
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// isNaN reports whether x is a NaN without requiring the math package.
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// This will always return false if T is not floating-point.
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func isNaN[T Ordered](x T) bool {
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return x != x
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}
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