/// Checks whether 'word' is in 'text', but not inside a word.
let isIn (text: string) (word: string) =
    let isSep c = not (Char.IsLetterOrDigit(c))

    let mutable index = 0
    let mutable cont = true

    while cont && index <> -1 do
        index <- text.IndexOf(word, index, StringComparison.CurrentCultureIgnoreCase)
        if index <> -1 then
            if (index = 0 || isSep text.[index - 1]) && (index + word.Length = text.Length || isSep text.[index + word.Length]) then
                cont <- false
            else
                index <- index + 1
    not cont