I was reading about some development interview practices, specifically about the technical questions and tests asked at interviews and I've stumbled quite a few times over sayings of the genre "Ok you solved the problem with a while loop, now can you do it with recursion", or "everyone can solve this with a 100 lines while loop, but can they do it in a 5 lines recursive function?" etc.

My question is, is recursion generally better than if/while/for constructs?

I've honestly always thought that recursion is not to be preferred, because it's limited to the stack memory which is a lot smaller than the heap, also doing a great number of function/method calls is suboptimal from a performance standpoint, but I may be wrong...

Recursion is not intrinsically better or worse than loops - each has advantages and disadvantages, and those even depend on the programming language (and implementation).

Technically, iterative loops fit typical computer systems better at the hardware level: at the machine code level, a loop is just a test and a conditional jump, whereas recursion (implemented naively) involves pushing a stack frame, jumping, returning, and popping back from the stack. OTOH, many cases of recursion (especially those that are trivially equivalent to iterative loops) can be written so that the stack push / pop can be avoided; this is possible when the recursive function call is the last thing that happens in the function body before returning, and it's commonly known as a tail call optimization (or tail recursion optimization). A properly tail-call-optimized recursive function is mostly equivalent to an iterative loop at the machine code level.

Another consideration is that iterative loops require destructive state updates, which makes them incompatible with pure (side-effect free) language semantics. This is the reason why pure languages like Haskell do not have loop constructs at all, and many other functional-programming languages either lack them completely or avoid them as much as possible.

The reason why these questions appear so much in interviews, though, is because in order to answer them, you need a thorough understanding of many vital programming concepts - variables, function calls, scope, and of course loops and recursion -, and you have to bring the mental flexibility to the table that allows you to approach a problem from two radically different angles, and move between different manifestations of the same concept.

Experience and research suggest that there is a line between people who have the ability to understand variables, pointers, and recursion, and those who don't. Almost everything else in programming, including frameworks, APIs, programming languages and their edge cases, can be acquired through studying and experience, but if you are unable to develop an intuition for these three core concepts, you are unfit to be a programmer. Translating a simple iterative loop into a recursive version is about the quickest possible way of filtering out the non-programmers - even a rather inexperienced programmer can usually do it in 15 minutes, and it's a very language-agnostic problem, so the candidate can pick a language of their choice instead of stumbling over idiosyncracies.

If you get a question like this in an interview, that's a good sign: it means the prospective employer is looking for people who can program, not people who have memorized a programming tool's manual.
