How Can You Append Items to a Variadic Function Wrapper Without Memory Reallocation?

Variadic Function Wrappers: Appending Items Without Memory Reallocation

Variadic functions provide a convenient way to pass an arbitrary number of arguments to a function. However, when wrapping variadic functions, appending additional items can result in memory allocation. This article examines different approaches to avoid unnecessary memory allocation in such wrappers.

Inefficient Approaches

Attempting to extend the variadic slice directly using the ellipsis "..." operator (Approach 1) may result in "too many arguments" errors or type mismatch issues (Approach 2).

Approach 3 allocates a new slice to accommodate the additional items, which can be inefficient for frequent logging or debugging operations.

Efficient Approach

A more efficient approach involves using the append function to dynamically grow the slice without reallocation. The append function returns a new slice with the additional items appended to the existing slice.

<code class="go">func Debug(a ...interface{}) {
    if debug {
        fmt.Fprintln(out, append([]interface{}{prefix, sep}, a...)...)
    }
}</code>

This one-liner appends the prefix and separator to a slice created from the original variadic arguments (a) and passes the resulting slice to fmt.Fprintln. By leveraging the append function, this approach avoids memory reallocation while satisfying the variadic function's parameter requirements.

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