How to Efficiently Check Equality Between Three Values in Go?

Efficient Ways to Check the Equality of Three Values

In Go, comparing multiple variables for equality can be a challenge. While the straightforward approach of if a == b == c results in compilation errors, there are several alternative methods that offer elegant and efficient solutions.

The Clear and Concise Approach

The recommended and most concise way to determine if three values are identical is:

<code class="go">if a == b && a == c {
    fmt.Println("All 3 are equal")
}</code>

This method leverages the fact that Go returns a boolean when comparing two values, ensuring a clear and readable code.

Alternatives for Experimentation

While the above solution is optimal, there are various creative options one could explore for experimentation:

Map as a Set:

<code class="go">if len(map[interface{}]int{a: 0, b: 0, c: 0}) == 1 {
    fmt.Println("Via a map set: all 3 are equal")
}</code>

The concept behind this method is to add the values as keys to a map, and if they are all equal, the map contains only one key, resulting in a length of 1.

Arrays:

<code class="go">if [2]interface{}{a, b} == [2]interface{}{b, c} {
    fmt.Println("Via arrays: all 3 are equal")
}</code>

Arrays are inherently comparable, allowing us to compare three values using ==. This approach, however, is only suitable for comparing a specific number of values.

Tricky Map:

<code class="go">if map[interface{}]bool{a: b == c}[b] {
    fmt.Println("Via a tricky map: all 3 are equal")
}</code>

This method utilizes a map to assign the result of b == c to a key, and then accesses the value associated with the same key. If a == b, the result of b == c is returned, indicating equality.

Anonymous Structs:

<code class="go">if struct{ a, b interface{} }{a, b} == struct{ a, b interface{} }{b, c} {
    fmt.Println("Via anonymous structs: all 3 are equal")
}</code>

Nested structs are comparable, allowing us to compare three values with a concise syntax.

Slices:

<code class="go">if reflect.DeepEqual([]interface{}{a, b}, []interface{}{b, c}) {
    fmt.Println("Via slices: all 3 are equal")
}</code>

While slices themselves are not comparable, the reflect.DeepEqual() function can determine their equality, allowing us to compare their contents.

Helper Function:

<code class="go">func AllEquals(v ...interface{}) bool {
    if len(v) > 1 {
        a := v[0]
        for _, s := range v {
            if a != s {
                return false
            }
        }
    }
    return true
}</code>

This reusable function simplifies the comparison of multiple values by iteratively checking equality and returning a boolean result. It can be used with any number of variables.

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