Maps, `Equal`

Do two maps have the exact same keys and values? This can be discovered with a for-loop, but the maps.Equal func from the "maps" package can check in a more concise way.

Part of the generics implementation in Go, the "maps" package provides some helpful methods for handling maps with any key and value types. Equal, and EqualFunc, are some of the most useful.

Example

This program creates 3 maps (all with string keys and int values) and tests them with Equal and EqualFunc. The first 2 maps are exactly equal.

Part 1 We create the 2 maps with assignment statements. The string keys and "test" and "bird."

Part 2 We call maps.Equal which accesses the "maps" package method. We pass 2 arguments (the 2 maps) and it tells us the maps are in fact equal.

Part 3 We create another map, but this time it has the value 0 instead of 100 for the value of the "test" key.

Part 4 With maps.EqualFunc, we must pass a function that tells whether two values of different maps (at the same key) are equal.

package main

import (
    "fmt"
    "maps"
)

func main() {
    // Part 1: create 2 maps that have the same keys and values.
    map1 := map[string]int{}
    map1["test"] = 100
    map1["bird"] = 200

    map2 := map[string]int{}
    map2["test"] = 100
    map2["bird"] = 200

    // Part 2: use maps.Equal to test if the 2 maps are equal.
    if maps.Equal(map1, map2) {
        fmt.Println("Maps are equal!")
    }

    // Part 3: create a map with the same keys, but a different value.
    map3 := map[string]int{}
    map3["test"] = 0
    map3["bird"] = 200

    // Part 4: use maps.EqualFunc to add special logic to consider maps equal.
    if maps.EqualFunc(map2, map3, func(v1 int, v2 int) bool {
        // Consider a 0 value to always be equal.
        return v2 == 0 || v1 == v2;
    }) {
        fmt.Println("Maps are equal with EqualFunc")
    }
}Maps are equal!
Maps are equal with EqualFunc

With the maps package, we can access useful methods like Equal and EqualFunc, which make it easier to test maps for equivalence. Custom logic can be added with EqualFunc.

Maps, Equal

Example

Maps, `Equal`