The Hardest Test I Ever Gave (C++)

http://lbrandy.github.com/blog/2008/11/the-hardest-test-i-ever-gave-c/

by aroman • 13 years ago

32 57 13 years ago

lbrandy.github.com

rmserror• 13 years ago

This is crap.

1e: this is undefined behavior (-Wsequence-point) x can be literally anything.

3. a typical mistake that the compiler both warns about and that anyone who has taken a course on C should be able to immediately recognize

bonus 1. void main(int)???

DerekL• 13 years ago

Question 1 asks about syntax. The behavior of the code is irrelevant.

TwoBit• 13 years ago

Except for the the fact that the author writes: "for bonus points, if x is 1 before 1e, what is x after that line?"

adamnemecek4• 13 years ago

Oh, you came up with a shitty test (testing I'm not even sure what) to stroke your ego while probably turning some kids away from programming? And then you thought that a recollection of this experience was worth sharing with the world? I sarcastically applaud your efforts. But seriously you are a douche.

100984• 13 years ago

If the object of the course is to study C++, I say this is a good test, and it's not even that hard tbh.

adamnemecek4• 13 years ago

I did not say it was. But it's a shitty test regardless.

nhaehnle2• 13 years ago

In fairness, the author does recognize that he failed in giving a good test.

The thing is, those questions demonstrate a certain type of playfulness in dealing with the subject. It is not uncommon for good students to think of this type of questions when they design their first tests, precisely because those are the kinds of questions that they like to think about themselves. What they fail to recognize is that those questions are incredibly hard for others precisely because of their playfulness.

So those questions are useful for quickly recognizing really good students (students that are so good that they transcend the requirements of the course and can deal with the subject on this playful level), but they should only make up a very small portion of any test. And teachers should probably warn their students about this type of question...

chris_wot10• 13 years ago

Not really. To be honest, if anything it's good training. How many times have you seen an assignment operator in an if statement where a comparison operator was meant to be used?

Actually, now I think of it... all the questions were related to operators, except the last one which was a trick question. If all the questions bar one were in regards to operators only, then this isn't a particularly good test.

shin_lao• 13 years ago

I disagree. Question#5 and bonus Question#1 are good questions. Production bugs are often close to these.

It tests if a student is able to follow a program's logic with rigor. It tests if you don't interpret the code but actually read it "as is".

Question#1 and Question#2 are less intelligent.

Also, no template test? Are you testing C with classes or C++ ? ;)

daemin• 13 years ago

I found Question #1 to be bad, #2 is alright but coming close to just a 'trick' question. #5 is just a simple trick question, and I can see where people went wrong with it. Especially if they skimmed over the code, and in a high pressure test environment. The bonus question is reasonable and can be worked through, if it wasn't printing the string literals, which makes it just a mean trick question.

I think that's the problem with a lot of first time test (or interview) makers, they make their questions into trick/puzzle questions where they want the test taker to guess what the writer had in their mind.

--edited because I skimmed over the last question and assumed it was printing the values of the variables not the strings--

_pmf_2• 13 years ago

I'm truly sorry that learning a real language takes some more effort than Ruby-loving ADHD rockstar developers can muster.

antihero• 13 years ago

Screw that, I loved it when we'd get a "bonus test" that was actually really difficult.

leoh2• 13 years ago

Meh. I thought this was pretty easy. Where are the solutions?

100984• 13 years ago

You can use a compiler to find the solutions. Except maybe for 1e bonus part, the output won't tell you much in that case.

benihana• 13 years ago

Can I ask what the point of this comment is? Obviously one can use a compiler to find the solutions. OP was most likely asking because he didn't want to do that.

jre• 13 years ago

This reminds me about an undergrad C course I had. One test was about printf formatting. We were given a serie of crazy format strings (using format specifier I've never encountered again since) and had to know what it would output. This was the most stupid test I've ever had.

There was a similar one about pointers. We called it "Star Wars".

gregorkas• 13 years ago

http://xkcd.com/138/

chris_wot10• 13 years ago

A test about pointers is not stupid. A test about printf formatters is.

_pmf_2• 13 years ago

> A test about pointers is not stupid. A test about printf formatters is.

Obviously you did not have the joy of working with people who write their own byzantine 1k LoC formatting code for cases that would have been perfectly covered by printf (and yes, this was on a system where a printf implementation was available).

ankitml• 13 years ago

You are cruel!!

tommys• 13 years ago

Nonsense test.

rorrr5• 13 years ago

Without a compiler, or google, haven't touched C++ in years:

1a) will give an error

2a) 2

2b) -10

2c) 4

2d) This is clever, haha. Answer: 5

2e) true (or 1)

5) "This is the answer." because of

    if (y = z)

Bonus) jk

raverbashing3• 13 years ago

1a) not so sure, because it could be x+(+3)

But yeah, gcc throws an error

If you put the parenthesis it works

chris_wot10• 13 years ago

He didn't put it into parenthesis.

rorrr5• 13 years ago

It also works if you add a space:

    x+ +3;

I always thought the unary plus operator is a complete waste, and shouldn't be implemented. I can't imagine a situation when it's needed.

EDIT: technically, it's a bug in GCC. It sees "x++" and assumes it's a unary increment, followed by a hardcoded 3. It definitely should consider that it's an addition followed by a unary plus (which has higher precedence than addition). But I guess it's an ambiguous syntax, and GCC is just being strict.

beambot2• 13 years ago

Perfect reminder of why I don't use C / C++ anymore. I had a teacher (highschool, IIRC) who made similar exams... He had the gall to call his course "computer science." I called it a waste of time, effort, and brainpower. I hate to think about how many computer-loving students he ruined.

OP, you did your students a disservice. You should've just assigned a "practicum" exam instead.

bnegreve• 13 years ago

1. There is no such a thing as C / C++. "Real" C++ is closer to other OO languages than it is from C.

2. It is not because a language is not a good option for teaching that it isn't worth using.

BTW After hours of debate, I still think that C is not a bad option for teaching purposes, mainly because it has a very simple syntax and almost NO api which generally introduce confusion.

beambot2• 13 years ago

1. I learned the two languages contemporaneously. They were commonly referred to as C / C++. I used C mostly for embedded/systems programming. I don't know what "real" C++ means... but to be fair, the last time I really used it was pre-STL.

2. OK. (I didn't make that claim, did I?) C / C++ has it's uses. I use it when I have to (embedded systems, systems programming, and performance). But I don't use it willingly.

I TA'd a course in C for EE's. It was fine. I think it probably helped them in many ways. Anecdote: My favorite course as an undergrad was building our own wire-wrapped 8086 computer. You quickly learn to appreciate assembly (versus manually loading registers), and then quickly learn to appreciate the C compiler.

pimentel• 13 years ago

I learned programming in C. I really think it is important to learn all the data structures internal functioning (coding your own linked lists or hash-tables), learning how memory in a program really works, what is the difference between a 4 byte-type variable versus a 1 byte one, etc

olalonde• 13 years ago

I would probably have assumed that "question #5" and "Bonus Question #1" had typos and failed those questions.

    if (y = z)

and

    cout << 'j' << 'k';

raverbashing3• 13 years ago

(a = b) inside an if (inside a test) is never a typo!!

That get me to think "this is the evillest thing I can imagine" =)

nhaehnle2• 13 years ago

You should always either ask to clarify or, if that is not possible, go with the literal statement of the question, and explicitly say so on your test paper. Any professor worth his/her salt will accept that and think even more highly of you, because they will recognize that you are able to think about the question on a higher level than most students.

If, on the other hand, you just silently "correct" the question in your mind, you will fail - especially in a course on programming, because the point is exactly that you have to learn to deal with computers that do not silently "correct" the program that you give them.

Toenex• 13 years ago

These are great tests... for a compiler.

Sharlin• 13 years ago

1c is cruel. One can hardly expect freshmen to understand the difference between a syntax error and a semantic error. Depending on the context, the line may be perfectly valid, or it may not.

chris_wot10• 13 years ago

Not a single question about templates. Your test was not hard enough.

friendly_chap• 13 years ago

You are one of the reasons why education sucks in general.

aroman• 13 years ago

Just so everyone's clear, I am not the author of this blog post. I had replaced the I in the title with [He], but a. Mod must have annoyingly edited it out. I hope people realize that.

The Hardest Test I Ever Gave (C++)

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