How to check if two slices are equal

Published Thu 6 Jul, 2023
Last updated Wed 16 Aug, 2023
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If you use the == or != comparison operators you can only compare slices to nil.

So how do you check if two slices are equal?

Well.. that depends on what you mean by “equal slices”. But often you want to check if slices are of the same length and have equal elements at the same indices.

Depending on your Go version you can:

If you are using a Go version that does not support generics, you can always implement your own EqualSlices function. See the example below:

main.go
package main

import (
	"fmt"
	"slices"
)

func main() {
	x := []string{"🙈", "🙉", "🙊"}
	y := []string{"🙈", "🦍"}

	fmt.Println("slices.Equal:")
	fmt.Println("x equal to y?", slices.Equal(x, y))
	fmt.Println("y equal to x?", slices.Equal(y, x))
	fmt.Println("x equal to x?", slices.Equal(x, x))
	fmt.Println("y equal to y?", slices.Equal(y, y))

	fmt.Println("---")

	fmt.Println("EqualSlices:")
	fmt.Println("x equal to y?", EqualSlices(x, y))
	fmt.Println("y equal to x?", EqualSlices(y, x))
	fmt.Println("x equal to x?", EqualSlices(x, x))
	fmt.Println("y equal to y?", EqualSlices(y, y))
}

// EqualSlices checks if two slices have equal contents.
// For two slices to be equal:
// - They need to have the same number of elements.
// - Each element must be equal using the == operator.
func EqualSlices(s1, s2 []string) bool {
	if len(s1) != len(s2) {
		return false
	}

	for i, v := range s1 {
		if s2[i] != v {
			return false
		}
	}

	return true
}

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