Does knowing a specific programming language matter?

This post is mostly inspired by a suggestion Steve McConnell makes in Code Complete: "Don't program in a language, program into it" (emphasis mine).


The traditional method of recruiting software developers is to go "We are writing our program in C++ so we should get a guy who does C++". I imagine many recruiters and companies use keyword filters on CVs to filter out candidates who don't have experience in the particular language used on the job. The basic premise of this post though, is that this is not necessarily going to get you the best man for the job.


My main points are:

• The time needed to learn a new language is shorter than it was and isn't that long
• 3 years doing 3 different languages is a better sign of a good and keen programmer than 3 years of 1 language
• The overhead of learning a new language becomes a smaller proportion over time and is overridden by the extra productivity of a "better" employee
• If you've only hired say, Ruby developers and then stop doing Ruby you can be in trouble

I should be clear and say that given 2 near-identical programmers, one with experience in the language you are using and one without, I would choose the one with experience in the language, but rather the point I'm making is that you shouldn't be afraid to hire someone who looks like a better programmer but doesn't have direct experience in the language.


A collegaue of mine recently said that you can grasp the basics of a language in about a month and start being confident and expressive in about 3 months and I agree. After that roughly 3 month stage, you start seeing diminshing returns on learning more particulars of that language (perhaps an example of the Pareto principle). The time taken to learn a language has dropped over the years, thanks to the wealth of information available on the internet in tutorials, blog posts and places like StackOverflow, as well as the reduction in the costs of publishing meaning more people are able to produce books on specific programming languages.


A good basing in a variety of languages, of different styles (eg OO vs functional, static vs dynamic typing) and a willingness to learn something new (I still don't quite believe that some people who were interviewed for my current role didn't want to learn JavaScript, I mean why wouldn't you want to learn something new?) are I believe, a better base for a productive programmer than just having experience in 1 language but for more years. This brings me to another point made in Code Complete applicable across all langauges (not just programming ones), that the language you know can actually affect the thoughts you are able to think. Being able to say "I know we're meant to be writing this in Java but there's a really easy and elegant way of doing it in Haskell" is of more value in my opinion that just steaming in and writing a sound Java implementation of every problem you come across. Importantly, experience in a variety of langauges is also a good sign that you've got someone who's interested in software development and does stuff outside of work rather than someone who just rolled into a say, Java job out of uni and then stayed in Java because that's what they'd done before and have never done any programming outside of work and education.


Now obviously, someone who's experienced in a language is going to be quicker to start writing in it than someone who isn't but that initial overhead will become a small proportion over the course of a long term employment (and hopefully you're hiring the kind of people you want to keep for a long time). The 3 month timescale I suggested above is obviously up for debate, but the argument here is based on the assumption that multi-language programmer will turn out to be more productive than the single-language programmer and thus cancel out the overhead, however large it is.


My final point is that hiring language specific programmers can seriously backfire if you decide to stop using the language. Kevin Rose of Digg raised this point at LeWeb conference where he said about hiring PHP developers to build out the Digg site "you end up with lots of PHP developers, but at some point, PHP isn’t a problem anymore and you are stuck with all of those developers". This is especially relevant I would think for startups, whose business direction is not as fixed as large corporations and may decide to pivot from say web development to iOS development and therefore suddenly need to be able to program in a different language.


Now obviously there will be some jobs where in-depth knowledge of the specifics of a language are going to be extremely useful, for instance in performance or safety critical applications (though many performance problems are best solved at the architectural level and so aren't very language specific anyway) but I don't believe that the majority of jobs are like that. Also I'm particularly biased in this discussion because I was hired into my current role as a JavaScript developer with no experience of JavaScript.