Chris M works for a “solutions provider”. Mostly, this means taking an off-the-shelf product from Microsoft or Oracle or SAP and customizing it to fit a client’s specific needs. Since many of these clients have in-house developers, the handover usually involves training those developers up on the care and maintenance of the system.

Then, a year or two later, the client comes back, complaining about the system. “It’s broken,” or “performance is terrible,” or “we need a new feature”. Chris then goes back out to their office, and starts taking a look at what has happened to the code in his absence.

I’ve had to write a few domain-specific-languages in the past. As per Remy’s Law of Requirements Gathering, it’s been mostly because the users needed an Excel-like formula language. The danger of DSLs, of course, is that they’re often YAGNI in the extreme, or at least a sign that you don’t really understand your problem.

XML, coupled with schemas, is a tool for building data-focused DSLs. If you have some complex structure, you can convert each of its features into an XML attribute. For example, if you had a grammar that looked something like this:

Just last week, I was teaching a group of back-end developers how to use Angular to develop front ends. One question that came up, which did suprise me a bit, was how to deal with race conditions and concurrency in JavaScript.

I’m glad they asked, because it’s a good question that never occurred to me. The JavaScript runtime, of course, is single-threaded. You might use Web Workers to get multiple threads, but they use an Actor model, so there’s no shared state, and thus no need for any sort of locking.

Anonymous sends us this little blob of code, which is mildly embarassing on its own:

    static StringBuilder vsb = new StringBuilder();
    internal static string IsValidUrl(string value)
    {
        if (value == null)
        {
            return "\"\"";
        }

        vsb.Length= 0;
        vsb.Append("@\"");

        for (int i=0; i<value.Length; i++)
        {
            if (value[i] == '\"')
                vsb.Append("\"\"");
            else
                vsb.Append(value[i]);
        }

        vsb.Append("\"");
        return vsb.ToString();
    }