"Programming language paradigms" are meaningless

Labels such as "object oriented language" and "functional language" (and "logic language", etc) have so many conflicting accepted interpretations that they are almost totally devoid of meaning.

In the programming mainstream there is a weasel word when talking about paradigms, and that is "purity". To illustrate: Smalltalk code uses block closures extensively, perhaps more frequently than Common Lisp. Common Lisp on the other hand has object orientation facilities more advanced than Smalltalk; multiple dispatch and multiple inheritance are supported. Yet, mainstream programmers hold the belief that Common Lisp is "functional", while at the same time you'd be hard-pressed to find a programmer who would deny that Smalltalk is "object oriented". Of course, one can say that both Smalltalk and CL are "hybrid" OOP/functional languages, and are not "pure".

So what is a "pure" OOP language then? Perhaps Java, C#, or C++? Of course this would be yet another, totally arbitrary re-interpretation of the term "OOP"; and we would find that such a paradigm was an evolutionary dead-end, lacking expressive power needed to solve many problems elegantly. Along similar lines, what the mainstream refers to as "pure" functional language, namely those without mutable state, are also insufficient -- although the drawbacks of statelessness are overblown, there are definite drawbacks, such as the difficulty of implementing an interactive development environment in such a language.

Languages which confine themselves to one paradigm (or the mainstream definition thereof) also suffer in terms of implementation elegance, and invariably must step outside the language to describe themselves. Java cannot express its own control structures; purely functional languages have a hard time modeling low-level system-building constructs such as dynamic compilers and code replacement. So taking a mainstream concept of a "paradigm" is certainly not the path to follow for a language implementor.

There is really only one context where such labels make sense, and that is if we look at the history of programming languages. Certain ideas and the continuation of threads of research that gave us Simula, Smalltalk, C++, CLOS, Self, StrongTalk and Java could be described as "the object oriented movement", even if the languages in the list are as varied as a list consisting of ML, Prolog, SQL and FORTH. Certainly any language being developed today, unless it manages to be a total clone of a predecessor, does not belong to the part of history referred to by any existing programming paradigm in common use.

New language implementations (the interesting ones, anyway) instead aspire to implement the designer's vision of what good programming is; not a pre-existing set of ideas. I'm always looking around at new language projects, and there are many interesting ones out there. However when I see something with C-derived syntax, I groan. It probably means the semantics don't offer anything new either.