How Does Go Check for Element Membership Without an 'if x in' Construct?

Go's Approach to "if x in" Construct

Go offers various approaches to checking if an element exists within an array or checking membership. While it doesn't have an explicit "if x in" construct like Python, it provides a few alternatives depending on the version and data structure used.

1. Using Slices.Contains (Go 1.18 and Later)

For Go 1.18 and later versions, the slices.Contains method offers a direct and efficient solution. It takes an array or slice as input and checks if the specified element is present.

arr := []string{"a", "b", "c"}
if slices.Contains(arr, "b") {
    // Element is present
}

2. Iterating Over the Array (Before Go 1.18)

Prior to Go 1.18, there wasn't a built-in operator to check membership. Instead, a custom function could be created to iterate over the array:

func stringInSlice(a string, list []string) bool {
    for _, b := range list {
        if b == a {
            return true
        }
    }
    return false
}

3. Using a Map for Membership Checks

If iterating over the entire list is undesirable, using a map instead of an array or slice can provide a more efficient solution for membership checks:

visitedURL := map[string]bool {
    "http://www.google.com": true,
    "https://paypal.com": true,
}
if visitedURL[thisSite] {
    fmt.Println("Already been here.")
}

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