Use append to concatenate slices

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Metadata

ID: go-best-practices/concatenate-slices

Language: Go

Severity: Info

Category: Best Practices

Description

Programmers should avoid writing for i := range y { x = append(x, y[i]) } and use x = append(x, y...) instead.

Here are a few reasons why:

Simplicity and readability: The x = append(x, y...) expression is more concise and clearer in its intent. It directly appends all elements of y to x without the need for an explicit loop with index access. It is easier to read and understand for other developers.
Performance: Using the x = append(x, y...) syntax is generally faster and more efficient than iterating over each element of y using a for loop. The implicit use of variadic arguments in append reduces memory allocations and improves performance.
Avoiding index access: By using x = append(x, y...), you eliminate the need for manual index access y[i] and let the built-in append function handle the internal implementation efficiently.
Consistency: Using x = append(x, y...) for concatenation is consistent with other idiomatic Go code. It is a widely accepted practice and is commonly used in the Go community.

By adopting the x = append(x, y...) approach, programmers can simplify their code, improve performance, and adhere to Go’s idiomatic style. It enhances code readability, reduces the chance of typographical errors, and promotes efficient slicing and concatenation.

Non-Compliant Code Examples

func main() {
    for i := range y {
        x = append(x, y[i])
    }
}

Compliant Code Examples

func main() {
    x = append(x, y...)

    for _, e := range y {
        x = append(x, e)
    }
}