Programming languages are living phenomena: They're born; the lucky ones that don't die in infancy live sometimes long, fruitful lives; and then they inevitably enter a period of decline. Unlike real life, the decline can last many, many years as the presence of large legacy code bases means practiced hands must tend the code for decades. The more popular the language once was, the longer this period of decline will be.

The emergence of a new language, however, is almost always tied to needs in a specific sector -- for example, Ruby's sudden adoption when Ruby on Rails appeared, and Objective-C's surge, which began in 2007 when the iPhone first shipped. So, understanding the fluctuations as well as the trends -often delivers valuable insights into the current coding issues.

The most recent processor phenomenon -- the transition from the multicore to many-core era -- was expected to set the stage for the emergence of functional languages, which fit well with concurrent programming. But most surveys from 2012 still show no major breakthrough. If a functional language does separate from the pack, the leading candidates are Scala and Clojure, with Scala enjoying the greater adoption right now. This per Ohloh's language figures, which cover all open source projects, and Google trends, which indicate search traffic. On the venerable Tiobe index, which tracks the number of Web pages that mention a given language, Haskell, Erlang, and Scala are effectively tied and ahead of Clojure.