cmp

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原文：https://pkg.go.dev/cmp@go1.24.2

注意
从go1.21.0开始才有该包。

概述

Package cmp provides types and functions related to comparing ordered values.

cmp包提供了与比较有序值相关的类型和函数。

常量

This section is empty.

变量

This section is empty.

函数

func Compare

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func Compare[T Ordered](x, y T) int

Compare returns

Compare函数返回以下值：

-1 if x is less than y,
如果x小于y，返回-1；
 0 if x equals y,
 如果x等于y，返回0；
+1 if x is greater than y.
如果x大于y，返回+1。

For floating-point types, a NaN is considered less than any non-NaN, a NaN is considered equal to a NaN, and -0.0 is equal to 0.0.

对于浮点类型，NaN被视为小于任何非NaN，NaN被视为等于NaN，-0.0等于0.0。

func Less

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func Less[T Ordered](x, y T) bool

Less reports whether x is less than y. For floating-point types, a NaN is considered less than any non-NaN, and -0.0 is not less than (is equal to) 0.0.

Less函数报告x是否小于y。对于浮点类型，NaN被视为小于任何非NaN，并且-0.0不小于（等于）0.0。

func Or <-go1.22.0

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func Or[T comparable](vals ...T) T

Or returns the first of its arguments that is not equal to the zero value. If no argument is non-zero, it returns the zero value.

Or 函数返回其第一个不等于零值的实参。如果没有实参为非零，则返回零值。

Or Example

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package main

import (
	"cmp"
	"fmt"
)

func main() {
	// Suppose we have some user input
	// that may or may not be an empty string
	userInput1 := ""
	userInput2 := "some text"

	fmt.Println(cmp.Or(userInput1, "default"))
	fmt.Println(cmp.Or(userInput2, "default"))
	fmt.Println(cmp.Or(userInput1, userInput2, "default"))
}

Output:

default
some text
some text

Or Example (Sort)

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import (
	"cmp"
	"fmt"
	"slices"
)

func main() {
	type Order struct {
		Product  string
		Customer string
		Price    float64
	}
	orders := []Order{
		{"foo", "alice", 1.00},
		{"bar", "bob", 3.00},
		{"baz", "carol", 4.00},
		{"foo", "alice", 2.00},
		{"bar", "carol", 1.00},
		{"foo", "bob", 4.00},
	}
	// Sort by customer first, product second, and last by higher price
	slices.SortFunc(orders, func(a, b Order) int {
		return cmp.Or(
			cmp.Compare(a.Customer, b.Customer),
			cmp.Compare(a.Product, b.Product),
			cmp.Compare(b.Price, a.Price),
		)
	})
	for _, order := range orders {
		fmt.Printf("%s %s %.2f\n", order.Product, order.Customer, order.Price)
	}

}

Output:

foo alice 2.00
foo alice 1.00
bar bob 3.00
foo bob 4.00
bar carol 1.00
baz carol 4.00

类型

type Ordered

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type Ordered interface {
	~int | ~int8 | ~int16 | ~int32 | ~int64 |
		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
		~float32 | ~float64 |
		~string
}

Ordered is a constraint that permits any ordered type: any type that supports the operators < <= >= >. If future releases of Go add new ordered types, this constraint will be modified to include them.

Ordered是一个约束，它允许任何有序类型：任何支持< <= >= >操作符的类型。如果Go的未来版本添加了新的有序类型，此约束将被修改以包含它们。

Note that floating-point types may contain NaN (“not-a-number”) values. An operator such as == or < will always report false when comparing a NaN value with any other value, NaN or not. See the Compare function for a consistent way to compare NaN values.

请注意，浮点类型可能包含NaN（“非数字”）值。当将NaN值与其他值（NaN或非NaN）进行比较时，==或<等操作符将始终报告false。请使用Compare函数作为比较NaN值的一致方式。

最后修改 April 2, 2025: 更新 (a79f9c5f)