For an interesting dive into one formal definition of the expressiveness of different features, see [1]. It defines expressiveness of features by asking questi

For an interesting dive into one formal definition of the expressiveness of different features, see [1]. It defines expressiveness of features by asking questions like (I'm really simplifying here) "If I add this feature to my language and start plugging it into programs that didn't use that feature before, can I write any programs that I couldn't before?" This is a useful definition because a feature like an enhanced for-loop doesn't have global effects on the program if it's plunked into some local context -- the same program could have been written without it. But adding something like, say, exceptions does have interesting nonlocal effects, and allows for differently-shaped computations than before. The useful point here is that the feature is added as an incremental change on an already-existing language, so its effects can be measured relative to the original language. The original and extended language can both be Turing-complete, and this is still a useful definition. [1] http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.51.4656 http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.51.4...