How Can I Efficiently Reference the Same Parameter Multiple Times in fmt.Sprintf?

Efficiently Referencing the Same Parameter in fmt.Sprintf

When working with fmt.Sprintf, it is common to encounter situations where you need to reference the same parameter multiple times within the format string. While duplicating the parameter may seem straightforward, it can be inefficient and introduce redundant code.

Solution: Utilizing Explicit Argument Indexing

To address this issue, fmt.Sprintf provides a solution known as "explicit argument indexing." This technique allows you to refer to a specific argument by its index within the format string. By using the format specifier [n] immediately before the formatting verb, you can specify which argument should be formatted.

For example, consider the following code:

package main

import "fmt"

func main() {
    v := "X"

    // Use explicit argument indexing to reference v four times
    fmt.Printf(
        `CREATE TABLE share_%[1]v PARTITION OF share FOR VALUES IN (%[1]v);
CREATE TABLE nearby_%[1]v PARTITION OF nearby FOR VALUES IN (%[1]v);`,
        v, v, v, v,
    )
}

In this example, instead of passing v four times, we use [1]v within the format string, which effectively references the first argument four times. The result is a concise and efficient format string:

CREATE TABLE share_X PARTITION OF share FOR VALUES IN (X);
CREATE TABLE nearby_X PARTITION OF nearby FOR VALUES IN (X);

Benefits of Explicit Argument Indexing

Using explicit argument indexing offers several benefits:

• Reduced code duplication for cleaner and more maintainable code.
• Improved performance by avoiding the unnecessary copying of arguments.
• Increased flexibility by allowing for the dynamic specification of which argument should be formatted.

Conclusion

Explicit argument indexing in fmt.Sprintf provides an efficient and flexible way to reference the same parameter multiple times within a format string. This technique not only simplifies code but also enhances performance, making it a valuable tool for working with string formatting in Go.

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