How Can I Reuse the Same Parameter Multiple Times in a Go fmt.Sprintf Format String?

How to Refer to the Same Parameter Multiple Times in a fmt.Sprintf Format String

In Go, the fmt package provides a convenient way to format strings using the Sprintf function. However, it can be cumbersome to specify the same parameter multiple times within the format string.

Consider the following example:

func getTableCreationCommands(v string) string {
    return `
        CREATE TABLE share_` + v + ` PARTITION OF share FOR VALUES IN (` + v + `);
        CREATE TABLE nearby_` + v + ` PARTITION OF nearby FOR VALUES IN (` + v + `);
    `
}

Here, we have to repeat the parameter 'v' four times to create the SQL commands. Instead of this verbose approach, we can use explicit argument indexes to refer to the same parameter multiple times within the format string.

import "fmt"

func getTableCreationCommands(s string) string {
    return fmt.Sprintf(`
        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);
    `, s)
}

func main() {
    fmt.Println(getTableCreationCommands("X"))
}

In this modified function, we enclose the argument index [1] within square brackets before the formatting verb (%v), indicating that we want to use the first argument passed to Sprintf, which is the string "X" in this case. The Playground link for this snippet is https://play.golang.org/p/fKV3iviuwll.

Using explicit argument indexes allows us to pass the parameter only once and reference it as needed within the format string, resulting in a more concise and readable implementation.

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