http://ayende.comAyende @ RahienCopyright (C) Ayende Rahien 2004 - 2021 (c) 202660The purpose of interview questions is this: i want a view into how the candidate thinks and solves problems in a pressure situation. In that vain, this question is useful from the perspective of how a candidate deals with things like pointless questions or a fool in a 'management' role. Does he/she stay composed? http://ayende.com/4498/code-twisters-the-functional-loop#comment24http://ayende.com/4498/code-twisters-the-functional-loop#comment24Mon, 21 Jun 2010 07:55:12 GMTI would Func <int,> nextLevel = new Func <int,> (x => x - 1); and have no issues with increment/decrement precedence. http://ayende.com/4498/code-twisters-the-functional-loop#comment23http://ayende.com/4498/code-twisters-the-functional-loop#comment23Sat, 15 May 2010 21:06:48 GMT11 times ? http://ayende.com/4498/code-twisters-the-functional-loop#comment22http://ayende.com/4498/code-twisters-the-functional-loop#comment22Fri, 14 May 2010 01:12:10 GMTThe purpose of interview questions is this: i want a view into how the candidate thinks and solves problems in a pressure situation. In that vain, this question is useful from the perspective of how a candidate deals with things like pointless questions or a fool in a 'management' role. Does he/she stay composed? As a candidate I respect problems like the counterfeit coin, anagrams, etc as they are implicitly respecting me in asking them. Questions like these throw the bozo bit on the employer and raises more red flags than it clears. http://ayende.com/4498/code-twisters-the-functional-loop#comment21http://ayende.com/4498/code-twisters-the-functional-loop#comment21Thu, 13 May 2010 18:34:36 GMTTo me, ALL interview questions are valid. Whether or not they're GOOD questions has less to do with the question than with how the interviewer uses the answer. In this example, if the interviewer's simply trying to gauge level of factual knowledge, and you get a plus for right and a minus for wrong, then it's a bad question. On the other hand, if the interviewer is using the question to evaluate the developer's thinking processes, it's a perfectly valid question. Now consider - if that's what the interviewer is doing, everyone who says "You're never going to see that in production code, so it's a terrible question, and you're just prejudicing the interview process against anyone who's never done C" is totally off-base: the candidate who's never done C is AT AN ADVANTAGE, because he gets to show off his thought processes, and the interviewer will be able to accurately evaluate the candidate's problem-solving process. A developer who's got the entire language down cold, though, will just spit out the answer, and will have to sit through another (and maybe another, and another) question before the interviewer can get the information he wants. Don't discard questions out of hand because you THINK you know the way in which the interviewer is going to use them. Just because the question strikes you as contrived, artificial, or pointless, doesn't mean it really is - the interviewer may just be doing more than you give him credit for. http://ayende.com/4498/code-twisters-the-functional-loop#comment20http://ayende.com/4498/code-twisters-the-functional-loop#comment20Thu, 13 May 2010 18:05:24 GMTI think the more appropriate interview question would be: This code causes an infinite loop. Why? http://ayende.com/4498/code-twisters-the-functional-loop#comment19http://ayende.com/4498/code-twisters-the-functional-loop#comment19Thu, 13 May 2010 17:41:50 GMTDamn, my comment got flagged as spam :) I just wanted to say: this is how Ayende will stop being Ayende eventually. By embarrassing himself to the point of not making his bold opinions public anymore. http://ayende.com/4498/code-twisters-the-functional-loop#comment18http://ayende.com/4498/code-twisters-the-functional-loop#comment18Thu, 13 May 2010 17:21:28 GMTI agree that this is a bad question if it is strictly to see how good of a language lawyer the candidate is. However, I can see it being useful for watching how someone goes about solving a problem as Bryan pointed out. http://ayende.com/4498/code-twisters-the-functional-loop#comment17http://ayende.com/4498/code-twisters-the-functional-loop#comment17Thu, 13 May 2010 15:31:05 GMTHorrible interview question... Its the kind of thing that will catch 90% of developers out there on the spot, but 90% of the people who got caught would find it within 1 minute with a debugger running, if it came up at work in real life. Plus the whole x--, --x thing is left over from the C/C++ days it really serves no purpose in C# code compared to the much simpler x += 1 construct.. So it filters out people with something that is totally outside of real world usuage, that would easily be resolved in the real world, without testing their true understanding. http://ayende.com/4498/code-twisters-the-functional-loop#comment16http://ayende.com/4498/code-twisters-the-functional-loop#comment16Thu, 13 May 2010 14:33:54 GMT@Jonty IMO the reason this is a good interview question is when you hire a new person, you are going to have them maintaining a bunch of code that they didn't write, and that there is a good chance that they would "have done it differently". That's how this works. So, when the developer is confronted with code that they aren't familiar with, how do they work through the code, and figure out what it does. Do they have critical thinking, and reasoning skills. They don't have to get it right, the goal isn't to see if they get it right, but rather to watch how they reason, and talk through it. Obviously a unit test, or the debugger could get the answer, and it's good to use tools to solve the problems efficiently, but as developers, we are problem solvers, and you want to exercise those skills in an interview as well as the candidates technical skills. http://ayende.com/4498/code-twisters-the-functional-loop#comment15http://ayende.com/4498/code-twisters-the-functional-loop#comment15Thu, 13 May 2010 14:19:26 GMTI think this is a classic case of unreadable code dressed up as clever code. What's the point? http://ayende.com/4498/code-twisters-the-functional-loop#comment14http://ayende.com/4498/code-twisters-the-functional-loop#comment14Thu, 13 May 2010 12:19:25 GMTI don't think it would make a good interview question. Good interview questions aren't about catching people out. A good developer might be caught out by some code, but would have unit tests that aren't. http://ayende.com/4498/code-twisters-the-functional-loop#comment13http://ayende.com/4498/code-twisters-the-functional-loop#comment13Thu, 13 May 2010 11:39:48 GMTResharper actually identifies it as a redundant decrement... http://ayende.com/4498/code-twisters-the-functional-loop#comment12http://ayende.com/4498/code-twisters-the-functional-loop#comment12Thu, 13 May 2010 11:28:41 GMTx => x-1 would also work. It's the return value that matters, not the decrement. http://ayende.com/4498/code-twisters-the-functional-loop#comment11http://ayende.com/4498/code-twisters-the-functional-loop#comment11Thu, 13 May 2010 10:53:13 GMTWhoops! Didn't see that level is set to what the lambda expression evaluates to. Ditto what others said about --x vs. x--. http://ayende.com/4498/code-twisters-the-functional-loop#comment10http://ayende.com/4498/code-twisters-the-functional-loop#comment10Thu, 13 May 2010 10:33:51 GMTI expect that lambda bodies, like bodies of other methods, use _copies of_ the arguments passed in (copies of value-type arguments or of references, but not copies of objects), so running nextLevel(level) has no side effects outside of itself--i.e., it decrements its local copy of level (x), not level itself. So Rafal is right. http://ayende.com/4498/code-twisters-the-functional-loop#comment9http://ayende.com/4498/code-twisters-the-functional-loop#comment9Thu, 13 May 2010 10:30:34 GMTInfinite. If you change the nextLevel func to Func <int,> nextLevel = new Func <int,> (x => --x); var x = 10; x = x++; Console.WriteLine(x); what will be printed ? ;) [weblogs.asp.net/.../..._2B002B00_-and-C_2300_.aspx](http://weblogs.asp.net/kennykerr/archive/2006/03/29/Increment-differences-in-C_2B002B00_-and-C_2300_.aspx) http://ayende.com/4498/code-twisters-the-functional-loop#comment8http://ayende.com/4498/code-twisters-the-functional-loop#comment8Thu, 13 May 2010 09:23:37 GMTinfinite... should be --x instead of x-- http://ayende.com/4498/code-twisters-the-functional-loop#comment7http://ayende.com/4498/code-twisters-the-functional-loop#comment7Thu, 13 May 2010 09:17:25 GMTIt will be an infinite loop ! Unless you define nextLevel this way : Func<int, int> nextLevel = new Func<int, int>(x => --x); nextLevel will always return level... http://ayende.com/4498/code-twisters-the-functional-loop#comment6http://ayende.com/4498/code-twisters-the-functional-loop#comment6Thu, 13 May 2010 09:16:47 GMTx-- http://ayende.com/4498/code-twisters-the-functional-loop#comment5http://ayende.com/4498/code-twisters-the-functional-loop#comment5Thu, 13 May 2010 09:16:34 GMT--x should do the trick. http://ayende.com/4498/code-twisters-the-functional-loop#comment4http://ayende.com/4498/code-twisters-the-functional-loop#comment4Thu, 13 May 2010 09:15:04 GMTShame this took so long to crack - should have got this straight off from my C++ days. http://ayende.com/4498/code-twisters-the-functional-loop#comment3http://ayende.com/4498/code-twisters-the-functional-loop#comment3Thu, 13 May 2010 09:14:59 GMTInfinitely, because the use of "x--" returns the value of x *before* decrementing x (locally), and hence nextLevel( n ) always returns the original value of n? http://ayende.com/4498/code-twisters-the-functional-loop#comment2http://ayende.com/4498/code-twisters-the-functional-loop#comment2Thu, 13 May 2010 09:14:35 GMTinfinite? http://ayende.com/4498/code-twisters-the-functional-loop#comment1http://ayende.com/4498/code-twisters-the-functional-loop#comment1Thu, 13 May 2010 09:12:40 GMT