Inefficient string comparison

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Metadata

ID: go-best-practices/inefficient-string-comparison

Language: Go

Severity: Info

Category: Best Practices

Description

In Go, it is recommended not to use strings.ToLower(s1) == strings.ToLower(s2) for case-insensitive string comparison. Instead, the strings.EqualFold(s1, s2) function should be used. Here’s why:

  1. Efficiency: Using strings.EqualFold(s1, s2) is more efficient because it avoids unnecessary string allocations. When you use strings.ToLower(s1), it creates a new lowercase string each time it is called. Comparing two lowercase strings using == (equality operator) then requires additional string comparison operations. In contrast, strings.EqualFold(s1, s2) performs a case-insensitive comparison directly without creating additional strings.
  2. Accurate case-insensitive comparison: strings.EqualFold(s1, s2) is specifically designed for case-insensitive string comparison. It takes into account different languages and ensures accurate results even with non-ASCII characters or special Unicode cases. In contrast, using strings.ToLower might not handle all edge cases correctly or consistently.
  3. Clarity and readability: By using strings.EqualFold(s1, s2), you convey your intention clearly and improve the readability of your code. The function’s name indicates that it performs a case-insensitive comparison, making the code easier to understand for future developers or maintainers.

Therefore, it is recommended to use strings.EqualFold(s1, s2) for case-insensitive string comparison in Go. This approach provides better performance, accuracy, and code clarity.

Non-Compliant Code Examples

func main() {
    if strings.ToLower(s1) != strings.ToLower(s2) {
        //
    }
    if !strings.EqualFold(s1, s2) {
        //
    }
}

func main() {
    if strings.ToLower(s1) == strings.ToLower(s2) {
        //
    }
}

Compliant Code Examples

func main() {
    if strings.EqualFold(s1, s2) {
        //
    }
}