If you're developing a fairly complex library for things such as image processing, machine learning, numerics, linear algebra, etc., then I think that C/C++ is

If you're developing a fairly complex library for things such as image processing, machine learning, numerics, linear algebra, etc., then I think that C/C++ is the way to go. Most languages have some sort of FFI to interact with C, many are even designed explicitly to work with C (such as Cython). C++ is in a similar situation (though compiler support on esoteric processors such as DSPs is still not quite there yet), and it's fairly easy to get a C-compatible API. If you write your library in Perl, guess what, only people writing Perl will use it. If you write it in Java, well, maybe the Scala folk will wrap it up, or the Jython folk, but you won't get any people writing in Ruby to use it. If you write it in C++, you can provide efficient bindings to any of those languages. For an example, look at FFmpeg or ImageMagick. They are libraries that just _won't die_, no matter how hard people have tried. My god, ImageMagick was written in 1987, and it now has Haskell bindings[0]! The only way to get that sort of longevity (and old code is good code, after all [1]) is to write in language that will outlast the ups and downs of the language or framework du jour, and C and C++ have proven to have that staying power. Yeah, they're terrible; I hate them. But there is a reason to use them. [0] http://hackage.haskell.org/package/imagemagick http://hackage.haskell.org/package/imagemagick [1] http://www.joelonsoftware.com/articles/fog0000000069.html http://www.joelonsoftware.com/articles/fog0000000069.html