How to Achieve Case-Insensitive Sorting of String Lists in Go?

Case Insensitive Sorting using sort.Strings() in Go

For case-insensitive sorting of string lists in Go, consider using sort.Slice(), which provides greater flexibility than sort.Strings().

Custom Function for Case-insensitive Comparison

You can pass a custom function to sort.Slice() to perform case-insensitive comparisons. The following function converts strings to lowercase before comparing them:

<code class="go">func lowercaseCompare(s1, s2 string) bool {
    return strings.ToLower(s1) < strings.ToLower(s2)
}</code>

Applying the Custom Function

To sort the list data case-insensitively using the custom function:

<code class="go">sort.Slice(data, lowercaseCompare)</code>

Example

Consider the string list data := []string{"A", "b", "D", "c"}. Sorting it case-insensitively using the custom function produces the result ["A", "b", "c", "D"].

Efficient Case-insensitive Sorting

The above approach allocates two new strings for each comparison. For large string lists, this can be inefficient. To improve performance, consider a rune-by-rune comparison:

<code class="go">func runeCompare(a, b string) bool {
    for {
        r1, s1 := utf8.DecodeRuneInString(a)
        r2, s2 := utf8.DecodeRuneInString(b)
        if r1 == utf8.RuneError || r1 == r2 {
            return s1 < s2
        }
        a = a[s1:]
        b = b[s2:]
    }
}</code>

Efficient Sorting with runeCompare()

To sort data efficiently:

<code class="go">sort.Slice(data, runeCompare)</code>

Alternative Solution: collate Package

For language- or culture-specific sorting, consider using the collate package. It provides locale-aware sorting capabilities.

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