How Can I Check for Slice Element Presence in Go Generically?

Generic Check for Slice Element Presence in Go

Determining if a slice contains a particular element is a common task in programming. However, the Go programming language lacks a built-in function for this purpose.

One approach is to use the interface{} type:

<code class="go">func sliceContains(slice []interface{}, elem interface{}) bool {
    for _, item := range slice {
       if item == elem {
          return true
       }
    }
    return false
}</code>

However, this approach requires manually writing code for each data type, making it cumbersome.

Using Reflection for a Generic Solution

Fortunately, Go's reflection package allows for generic code that can handle any slice type:

<code class="go">func Contains(slice, elem interface{}) bool {

    sv := reflect.ValueOf(slice)

    // Check if slice is valid
    if sv.Kind() != reflect.Slice && sv.Kind() != reflect.Array {
        return false
    }

    // Iterate over slice elements
    for i := 0; i < sv.Len(); i++ {
        if elem == sv.Index(i).Interface() {
            return true
        }
    }

    // Element not found
    return false
}</code>

Performance Considerations

While the reflection-based approach is generic, it comes with a significant performance penalty compared to type-specific non-generic functions. Benchmarks have shown a 50-60x slowdown:

Generic: 730.23214 ns/op
Non-Generic: 13.15262 ns/op

Conclusion

While reflection offers a way to write generic code for slice element checking, it is important to weigh the performance trade-offs carefully. For scenarios where performance is critical, type-specific non-generic functions are highly recommended.

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