How to Elegantly Check Value Equality in Go?

Elegant Ways to Check Value Equality in Go

In Go, comparing the equality of multiple values requires careful consideration to avoid compile errors. While the straightforward approach of if a == b == c results in a syntax error, there are several elegant solutions to this problem.

1. Conjunction with Boolean Operations:

Condensing the comparison using the && operator offers a compact and readable approach:

<code class="go">if a == b && a == c {
    // All 3 values are equal
}</code>

2. Map Set Implementation:

Utilizing a map as a set can effectively determine value uniqueness, since equal values will result in a map with a single key-value pair:

<code class="go">m := map[interface{}]int{a: 0, b: 0, c: 0}
if len(m) == 1 {
    // All 3 values are equal
}</code>

3. Array Comparability:

Arrays in Go are comparable, offering a straightforward solution:

<code class="go">arr1 := [2]interface{}{a, b}
arr2 := [2]interface{}{b, c}
if arr1 == arr2 {
    // All 3 values are equal
}</code>

4. Tricky Map:

A creative approach involves using a map to assign a boolean value based on equality and then retrieving it using another key:

<code class="go">m := map[interface{}]bool{a: b == c}
if m[b] {
    // All 3 values are equal
}</code>

5. Anonymous Structs:

Structs are also comparable in Go, allowing for concise value comparisons:

<code class="go">s1 := struct{ a, b interface{} }{a, b}
s2 := struct{ a, b interface{} }{b, c}
if s1 == s2 {
    // All 3 values are equal
}</code>

6. (Named) Structs with a Helper Function:

Creating a custom helper function can enhance the elegance of struct comparisons:

<code class="go">type P struct{ a, b interface{} }

func AllEquals(s P, t P) bool {
    return s == t
}

// Usage:
if AllEquals(P{a, b}, P{b, c}) {
    // All 3 values are equal
}</code>

7. Slices with Reflect.DeepEqual():

Slices, being non-comparable, require the use of reflection to determine equality:

<code class="go">slice1 := []interface{}{a, b}
slice2 := []interface{}{b, c}
if reflect.DeepEqual(slice1, slice2) {
    // All 3 values are equal
}</code>

These solutions provide diverse methods to elegantly compare the equality of three values, catering to different preferences and code styles.

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