[wikfwikf]

I asked ChatGPT to write a function which takes a year as input and determines whether or not it's a leap year - a classic basic programming question. It answered perfectly. Of course, there are lots of examples of this code.

Then I asked it "Could you adapt the function so that it works on Venus, where years have 224 days?"

It offered me a new version of the function, which simply checks if the year is a multiple of 224. Apparently on Venus the number of days in a year and the frequency of leap years are the same number. It qualified the answer: "It's worth noting that this function is based on current knowledge and understanding of Venus..."

I asked it "What if we want the function to use Venus days as well as Venus years?"

It offered me the same function, except that a) the variable 'years' was now called 'days', and b) the modulus was changed from 224 to 224.701.

So I asked "Should the argument to the last function be a float or an integer?"

It gave me 3 pars of complete nonsense about how the difference between floats and integers affects the precision of calculating leap years (while again warning that the exact value of the Venus year might change).

ChatGPT does a very good imitation of a certain type of candidate I've occasionally interviewed, who knows almost nothing but is keen to try various tricks to bluff you out, including confidently being wrong, providing lots of meaningless explanation, and sometimes telling you that you are wrong about something. I have never hired anyone like this, but I've occasionally come close.

I have been trying various interview questions on ChatGPT, originally because my colleagues warned me that a candidate who was surreptitiously using it could ace almost any interview. I was skeptical and I have not been convinced.

But I think it's actually a great exercise to practice interviewing on it. If ChatGPT can answer your questions accurately (try to be fair and ignore its slightly uncanny tone), then you probably need better questions. If you are quite technical and put some thought into it, you should be able to come up with things which are both novel enough and hard enough that ChatGPT will simply flounder catastrophically. (I'm not referring to 'tricks' like the Venus question, but real questions on how to achieve something moderately complicated using code.) It's a really good reminder too that when we ask candidates to write code, we should examine and debug it in detail, then ask decent follow-up questions, rather than just accepting something that looks right.