John Carmack on mutable variables

There is a huge amount of syntactic sugar that has been added over the years that doesn't do whole lot IMO. It is often imported from other languages (usually JavaScript and/or Python).

e.g. Just a very simple example to illustrate the point

    if (customer != null)
    {
        customer.Order = GetCurrentOrder();
    }

vs

    if (customer is not null)
    {
        customer.Order = GetCurrentOrder();
    }

Is there really any benefit in adding "is/is not"? I would argue no. So I categorise that as being of "dubious benefit" and there are many similar small features, keywords etc. that get added each release where they might save a few lines of code somewhere but I've never seem them used that often.

In your sample there really is no benefit to using the "is" operator over just checking for null (assuming you haven't overloaded the "!=" operator). However, the "is" operator is a lot more powerful, you can match an expression against a pattern with it. Would you say that these samples show no benefit to using the "is" operator?

if (obj is string s) { ... }

if (date is { Month: 10, Day: <=7, DayOfWeek: DayOfWeek.Friday }) { ... }

https://learn.microsoft.com/en-us/dotnet/csharp/language-ref... https://learn.microsoft.com/en-us/dotnet/csharp/language-ref...

The issue is that I dislike the overall mentality of just adding a bunch of language features. Things just seem to be dumped in each release and I think to myself "When I am going to use that?".

> Would you say that these samples show no benefit to using the "is" operator?

I didn't say no benefit. I said dubious benefit.

I didn't really want to get into discussing specific operators, but lets just use your date example:

   if (date is { Month: 10, Day: <=7, DayOfWeek: DayOfWeek.Friday }) { ... }

This following would do the same thing before the is operator:

    static bool IsFirstFridayOfOctober(DateTime date)
    {
        return date.Month == 10
            && date.Day <= 7
            && date.DayOfWeek == DayOfWeek.Friday;
    }

And then:

    if IsFirstFridayOfOctober(date) {
       ...
    }

I understand it is more verbose. But do we really need a new operator for this? I was getting on fine without it.

Each release there seems to be more of these language features and half the time I have a hard time remembering that they even exist.

Each time I meet with other .NET developers either virtually or in Person they all seem to be salivating over this stuff and I feel like I've walked in on some sort of cult meeting.

I agree that they should not add new stuff lightly, but the "is" operator actually should be looked together with switch expression in the context of pattern matching. How else could you enable powerful and succint pattern matching in c#?

> In your sample there really is no benefit to using the "is" operator over just checking for null

Microsoft give the same example though. I understand what hes saying, theres conceptual overlap between is and ==. Many ways to do the same thing.

Why couldnt it just be...

if (obj == string s) { ... }

Arguments about whether the is and switch operators should exist is missing the forest for the trees. I am sure there are circumstances where it very useful.

It isn't any one language feature it is the mentality of both the developer community and Microsoft.

> I agree that they should not add new stuff lightly

It seems though kinda do though. I am not the first person to complain that they add syntactic sugar that doesn't really benefit anything.

e.g. https://devclass.com/2024/04/26/new-c-12-feature-proves-cont...

I have a raft of other complaints outside of language features. Some of these are to do with the community itself which only recognise something existing when Microsoft has officially blessed it, it is like everyone has received the official permission to talk about a feature. Hot Reload was disabled in .NET 6 IIRC for dubious reasons.

In Python '==' and 'is' are not the same thing. '==' checks for equality, 'is' for identity.

I am aware. I probably should have said "inspired".