What questions should an expert in STL be expected to answer, in an interview

Question

I was looking at a job posting recently and one of the requirements was that a person be a 9/10 in their knowledge of STL.

When I judge my skills, to me a 10 is someone that writes advanced books on the subject, such as Jon Skeet (C#), John Resig (JavaScript) or Martin Odersky (Scala).

So, a 9/10 is basically a 10, so I am not certain what would be expected at that level.

An example of some questions would be found at: http://discuss.joelonsoftware.com/default.asp?joel.3.414500.47

Obviously some coding will be needed, but should everything be expected to be memorized, as there is quite a bit in STL.

In some cases Boost libraries extend STL, so should it be expected that I would be using Boost also, as I may sometimes confuse which function came from which of the two libraries.

I am trying to get an idea if I can answer questions that would be expected of a STL expert, though it is odd that being a C++ expert wasn't a requirement.

UPDATE

After reflecting on the answers to my question it appears that what they may be looking for is someone that can see the limits of STL and extend the library, which is something I haven't done. I am used to thinking within the limits of what STL and Boost give me and staying within the lines. I may need to start looking at whether that has been too limiting and see if I can go outside the box. I hope they don't mean a 9 as Google does. :)

Answer 1

Funny -- I don't consider myself a 9/10 in STL (I used to be, but I'm a bit rusty now), and I do fully agree with @joshperry's important terminological distinguo (I've often been on record as berating the abuse of STL to mean "the parts of the C++ standard library that were originally inspired by SGI's STL"!-), yet I consider his example code less than "optimally STL-ish". I mean, for the given task "Put all the integers in a vector to standard out.", why would anyone ever code, as @joshperry suggests,

for(std::vector<int>::iterator it = intVect.begin(); it != intVect.end(); ++i)
    std::cout << *it;

rather than the obvious:

std::copy(intVect.begin(), intVect.end(), std::ostream_iterator<int>(std::cout));

or the like?! To me, that would kind of suggest they don't know about std::ostream_iterator -- especially if they're supposed to be showing off their STL knowledge, why wouldn't they flaunt it?-)

At my current employer, to help candidates self-rate about competence in a technology, we provide a helpful guide -- "10: I invented that technology; 9: I wrote THE book about it" and so on down. So, for example, I'd be a 9/10 in Python -- only my colleague and friend Guido can fairly claim a 10/10 there. STL is an interesting case: while Stepanov drove the design, my colleague Matt Austern did the first implementation and wrote "the" book about it, too (this one) -- so I think he'd get to claim, if not a 10, a 9.5. By that standard, I could be somewhere between 7 and 8 if I could take an hour to refresh (custom allocators and traits are always tricky, or at least that's how I recall them!-).

So, if you're probing somebody who claims a 9, grill them over the really hard parts such as custom allocators and traits -- presumably they wouldn't miss a beat on all the containers, algorithms, and special iterators, so don't waste much interview time on those (which would be key if you were probing for a 7 or 7.5). Maybe ask them to give a real-life example where they used custom traits and/or allocators, and code all the details of the implementation as well as a few sample uses.

BTW, if you're the one needing to cram on C++'s standard library at an advanced level, I'm told by knowledgeable and non-rusty friends that Josuttis' book nowadays is even more useful than my friend Matt's (unfortunately, I've never read Josuttis in depth, so I can't confirm or deny that - I do see the book has five stars on Amazon, which is impressive;-).