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Best Way to Check the Equality of Two Slices in Go!

Maheshwar Ligade's photo
Maheshwar Ligade
·May 6, 2023·

3 min read

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Table of contents

  • Method 1: Loop through the Slices
  • Method 2: Using reflect.DeepEqual()
  • Conclusion

In Go, checking the equality of two slices can be a bit tricky. Slices are a reference type in Go, which means that when we compare two slices with the == operator, we are comparing their references, not their contents. Therefore, to check whether two slices contain the same elements, we need to compare their values element by element.

Method 1: Loop through the Slices

One way to compare the equality of two slices is to loop through them and compare their values element by element. Here is an example:

package main

import "fmt"

func main() {
    slice1 := []int{1, 2, 3}
    slice2 := []int{1, 2, 3}

    if len(slice1) != len(slice2) {
        fmt.Println("Slices are not equal")
        return
    }

    for i, v := range slice1 {
        if v != slice2[i] {
            fmt.Println("Slices are not equal")
            return
        }
    }

    fmt.Println("Slices are equal")
}

In this example, we first compare the lengths of the two slices. If the lengths are not equal, we know that the slices are not equal. If the lengths are equal, we loop through the first slice and compare each element to the corresponding element in the second slice. If we find a pair of elements that are not equal, we know that the slices are not equal. If we make it through the loop without finding any unequal elements, we know that the slices are equal.

Method 2: Using reflect.DeepEqual()

Another way to compare the equality of two slices is to use the reflect.DeepEqual() function from the reflect package. This function tests for deep equality between two values, which means that it recursively compares the values of structs, arrays, slices, maps, and pointers.

Here is an example:

package main

import (
    "fmt"
    "reflect"
)

func main() {
    slice1 := []int{1, 2, 3}
    slice2 := []int{1, 2, 3}

    if reflect.DeepEqual(slice1, slice2) {
        fmt.Println("Slices are equal")
    } else {
        fmt.Println("Slices are not equal")
    }
}

In this example, we use reflect.DeepEqual() to compare the two slices. If the function returns true, we know that the slices are equal. If the function returns false, we know that the slices are not equal.

However, it is important to note that reflect.DeepEqual() has some limitations. For example, it does not correctly compare functions or channels, and it can have unexpected behavior when comparing floats or interfaces. Therefore, it is generally recommended to use the loop method shown in Method 1, especially for simple types like slices of integers.

Conclusion

When comparing the equality of two slices in Go, we need to compare their values element by element. The loop method is a reliable and efficient way to do this, especially for simple types. The reflect.DeepEqual() function is also an option, but it has some limitations and should be used with caution.

I hope this helps, you!!

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