Is Ruby a functional language?

Question

Wikipedia says Ruby is a functional language, but I\'m not convinced. Why or why not?

Answer 1

I submit that supporting, or having the ability to program in a language in a functional style does not a functional language make.

I can even write Java code in a functional style if I want to hurt my collegues, and myself a few months weeks on.

Having a functional language is not only about what you can do, such as higher-order functions, first-class functions and currying. It is also about what you cannot do, like side-effects in pure functions.

This is important because it is a big part of the reason why functional programs are, or functional code in generel is, easier to reason about. And when code is easier to reason about, bugs become shallower and float to the conceptual surface where they can be fixed, which in turn gives less buggy code.

Ruby is object-oriented at its core, so even though it has reasonably good support for a functional style, it is not itself a functional language.

That's my non-scientific opinion anyway.

Edit: In retrospect and with consideration for the fine comments I have recieved to this answer thus far, I think the object-oriented versus functional comparison is one of apples and oranges.

The real differentiator is that of being imparative in execution, or not. Functional languages have the expression as their primary linguistic construct and the order of execution is often undefined or defined as being lazy. Strict execution is possible but only used when needed. In an imparative language, strict execution is the default and while lazy execution is possible, it is often kludgy to do and can have unpredictable results in many edge cases.

Now, that's my non-scientific opinion.