I hate to be the arrogant know it all on Hacker News, but seriously, if you're writing c# and not using LINQ all the time, you need to catch up.
I'm tired of seeing people answer interview questions with anything _other_ than LINQ.
I'm tired of seeing people answer interview questions with anything _other_ than LINQ.
That a C# developer can seriously say they're not up to speed with "new stuff" like LINQ (2005) and dynamic (2008) in 2013 is kind of ridiculous. What they mean is that they figured out how to map what they learned about Java in school into C#'s syntax and now they're done learning.
That said, not all questions are best solved with it, but it certainly has made working with enumerables much easier.
I'd like to aee people using the right tools for the job.
The HR interviewer followed up my answer asking about runtime and memory usage. While these are good questions, I got the feeling they didn't want to receive an answer using a single line of LINQ.
You don't sound arrogant, but rather sound naive. I agree that someone who recruits surely should have known about and have experienced LINQ significantly by now, but the notion that you should be using it "all the time" is absolute nonsense.
I avoid LINQ. I encourage others to avoid LINQ. It is almost always a sign of bad code.
LINQ is syntactical sugar over basic set operations. It is perfectly fine if you're doing naive activities, such as the example give -- a contrived example of brute forcing a problem, where two approaches of the same very basic need unsurprisingly yield the same complexity -- but it falls apart in real-world persistent code with considered algorithms and storage. In real long term code, it is usually the canary in the mineshaft telling you that the developers aren't using proper algorithms or storage.
In many large-scale projects it invariably turns into the performance nightmare that ends up causing whole rewrites.
Again, not because of LINQ itself, which of course can do basic operations like grouping and sorting as quickly as you could do "by hand", but that it makes it so easy to do those things that developers start to resort to that as a catch-all magical solution that is costless because how much could a line or two of code cost? -- a master List<stuff> that they just sort and group by and select from all over the code (O(n) * O(n) * O(n)...why not?). The end result is that the data structures and encapsulation that should have happened never did, so while it might seem more concise and obvious on a one-to-one comparison with a loop perspective, neither case should ever have happened.
LINQ is the gun by which a lot of terrible programmers are repeatedly shooting themselves in the foot with, all while gloating about their concise code.
The problem is that it makes it so conveniently easy to do brute-force tactics that....oh the horrible things I've seen...code gets littered with LINQ doing naive queries repeatedly over massive sets of data. Of course you need good coders and good code audits, but LINQ, I think, gives a unsupported sense of comfort that one is making good code (where if people had to code these as loops, it would become very evident very early on that maybe they should rethink their approach).
Correct me if I'm wrong, but the world is moving towards functional programming (i.e. LINQ) not away from it. Personally, I find LINQ far, far easier to read, write, and analyze. (On the other hand, I understand the deferred semantics and watch for warning signs like enumerating a sequence more than once.)
Honestly, a C# company avoiding LINQ sounds to me like the canary in the mineshaft telling you the company has programmers falling behind the times and doing things the hard way.
LINQ encourages the belief that set operations are free, such that you no longer have to concern yourself with concepts like memoization or appropriate structures. This has nothing to do with functional programming. Literally at all.
Basically, you're saying it's too easy to accidentally perform a computation twice by iterating through a sequence twice. Recurse on that problem and you get an exponential blowup.
That is actually a problem mostly unique to LINQ and it is really important that a programmer understand the deferred semantics. Some tools, e.g. ReSharper, will detect multiple enumerations and warn you about it. Judicious use of ToArray/ToList solves most issues with defer-splosion.
> "it falls apart in real-world persistent code with considered algorithms and storage"
> "it makes it so easy to do [grouping / sorting / etc] that developers start to resort to that as a catch-all magical solution that is costless because how much could a line or two of code cost"
With hindsight I know your issue is with LINQ's deferred non-memoized execution. It's really easy to enumerate a sequence twice, but every place you do that might add a factor of 2 to the runtime and so there's a danger of exponential blowup that must be avoided. But that's not what I see when I read the above.
The above reads as complaints about easy composability and worries about code monkeys failing to consider what the code they're writing will do. Those are standard "functional / high-level programming is bad" complaints. With hindsight I know that's not what you meant, but that's what it reads like.
LINQ's deferred execution was the right choice for performance, but it's the hardest one. You've got to know when to call .ToList(). I'm not denying that I've seen people evaluate the same expensive list 100 times, use a join when precomputing a Dictionary would have been much faster, close a connection before the result is actually evaluated. But I've never seen C++ programmers say you can make mistakes with pointers, so don't them.
Clojure's lazy sequences are guaraanteed to evaluate once, but that comes at the expense of storage. In particular, a query like the one in the original blog post will evaluate multiple intermediate lists that then need to be thrown away. And indeed, they've introduced reducers to address this, which behaves more like LINQ.
Why not fuse the operations, if the values are immutable?
It wouldn't be hard to make LINQ behave like Clojure, either.
Oh give me a break. My exact complaint about LINQ is the opposite -- that it makes expensive operations seem simple, which with all innovations in language means that mediocre programmers will start abusing it in all codebases.
LINQ has a place. To say that one should be using it "all the time", however, is exactly as I said -- a canary in a coal mine. The only time I've ever come across the extensive use of LINQ it has been in horrific code.
In fact, LINQ on Rx is a symptom of the classic LINQ issue -- don't have subscriber or source filtering, or coherent, useful events -- simply broadcast everything and through the magic, free filtering of LINQ all is solved in the consumer.