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Comment by dhsysusbsjsi | Hacker News Reader

(Small business owner): I prefer the "write me a function that squares a number" approach as the big filter. If they cannot do it, stop right there. If they write it and struggle a bit, stop there. If they write it at a normal or fast speed, continue. If they write an inlinable generic function that accepts anything that can be multiplied - things are looking really good.

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Interesting. My signal from a generic function is that this person tends to overarchitect, if my request was about squaring numbers specifically.

Some people love asking interview questions where they don't state all the requirements, so I suppose the idea is to see if the candidate can discover the "hidden criteria".

This also makes more sense in a language where number types need manual casting.

You can actually train these people by making them create quick POC projects until they become practical programmers. I would take the overarchitechting person.

If I heard this question, I'd be more confused than anything. The answer seems like it's just return x*x but I'd probably be more interested in why squaring numbers is so important that it needs a special function. Maybe I'm supposed to implement a BigInteger class or something like it...

> why squaring numbers is so important that it needs a special function

I've had pow2() in pretty much every codebase I'd worked on, ever. pow2(x1-x0) looks nicer and less error prone than (x1-x0)*(x1-x0), and less verbose and distracting than first separating to a local var as dx = x1-x0

What about using an actual vector library like Eigen? I wouldn’t dream of reimplementing basic maths like that.

Okay, let's role play this. Here's my Python solution:

    def square(n):
        return n**2

As a well prepared candidate, it took me seconds to write this. What did this tell you about me? Did I do anything wrong and if yes, what did you expect to see instead? What does this score out of 10 and why?

You are almost certainly better off just writing x*x whenever you need a square. A good programmer would point this out.

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