How Can I Modify a String in Go If It\'s Immutable?

String Alteration in Go: Resolving the "Cannot Assign to String" Error

Go strings are immutable, meaning they cannot be directly modified once created. This limitation often raises the error "cannot assign to new_str[i]" when attempting to alter a string's contents. To overcome this challenge and modify strings, an alternative approach is required.

One solution is to convert the string to a byte slice, which can be altered like an array. This technique allows for the replacement of characters within the string. The following code demonstrates this approach:

<code class="go">func ToUpper(str string) string {
    new_str := []byte(str)
    for i := 0; i < len(str); i++ {
        if str[i] >= 'a' && str[i] <= 'z' {
            chr := uint8(rune(str[i]) - 'a' + 'A')
            new_str[i] = chr
        }
    }
    return string(new_str)
}</code>

In this code, the string str is converted to a byte slice new_str. The byte slice is then iterated over, comparing each byte to the ASCII lowercase character range. If a lowercase byte is encountered, it is replaced with its uppercase ASCII equivalent. Finally, the modified byte slice is converted back to a string and returned.

This approach enables the alteration of strings in Go while maintaining their immutability. It provides a flexible and efficient way to manipulate strings in various contexts.

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