Thoughts on programming language fluency
If you have ever studied a second language yourself and then tried to use it outside the classroom, you know that there are three things you must master: how the language is structured (grammar), how to name things you want to talk about (vocabulary), and the customary and effective ways to say everyday things (usage).
When programmers enter the job market, the idea that, "We have the capability to learn any programming language," gets thrown around a lot. I now realize that this sentiment is irrelevant in many cases, because the deciding factor in the hiring process is more often time to fluency.
Time to fluency as a hiring factor
Let's say that there are two candidates, Fry and Laurie, interviewing for a programming position using Haskell. [*] Fry comes off as very intelligent during the interview process, but has only used OCaml and sounds like he mutabled all of the stuff that would make your head explode using monads. Laurie, on the other hand, couldn't figure out how many ping pong balls fit into Air Force One or why manhole covers are round, [†] but is clearly fluent in Haskell. Which one gets hired?
The answer to this question is another question: When are they required to be pumping out production-quality code?
Even working all hours of the day, the time to fluency for a language is on the order of weeks, independent of other scary new-workplace factors. Although books like Effective * can get you on the right track, fluency is ultimately attained through experience. Insofar as programming is a perpetual decision of what to make flexible and what to hard-code, you must spend time in the hot seat to gain necessary intuition — each language's unique characteristics change the nature of the game.
Everybody wants to hire Fry; however, Laurie will end up with the job due to time constraints on the part of the hiring manager. I'm pretty sure that Joel's interview notions are over-idealized in the general case:
Anyway, software teams want to hire people with aptitude, not a particular skill set. Any skill set that people can bring to the job will be technologically obsolete in a couple of years, anyway, so it’s better to hire people that are going to be able to learn any new technology rather than people who happen to know how to make JDBC talk to a MySQL database right this minute.
Reqs have to be filled so that the trains run on time — it's hard to let real, here-and-now schedules slip to avoid hypothetical, three-years-later slip.
Extreme Programming as catalyst
You remember that scene from The Matrix where Neo gets all the Kung Fu downloaded into his brain in a matter of seconds? That whole process is nearly as awesome as code reviews.
Pair programming and code reviews:
Trick your brain into learning everything faster through mild stress and the threat of looking noobish in your colleagues' eyes.
Give you the shoulders of language-fluent programmers to stand on as they push you in the right direction.
Back off in accordance with your fluency acquisition.
This is totally speculative, but from my experience I'd be willing to believe you can reduce the minimum-time-to-fluency by an order of magnitude with the right (read: friendly and supportive) Extreme Programming environment.
What I learned: When you create interfaces for everything (instead of base classes) it's almost less work to make a factory.
You know it's a hypothetical because it's a Haskell position. Bzinga!
The point is that Fry has the high ground in terms of perceived aptitude. I actually think most of the Mount Fuji questions are nearly useless in determining aptitude, though I do enjoy them. The referenced sentence is a poor attempt at a joke. ;-)