The literature on programming languages contains an abundance of informal claims on the relative expressive power of programming languages, but there is no framework for formalizing such statements nor for deriving interesting consequences. As a first step in this direction, we develop a formal notion of expressiveness and investigate its properties. To validate the theory, we analyze some widely held beliefs about the expressive power of several extensions of functional languages. Based on these results, we believe that our system correctly captures many of the informal ideas on expressiveness, and that it constitutes a foundation for further research in this direction.
in practice, turing complete doesn't necessarily mean powerful or equivalent. brainfuck and minecraft are turing complete but no one is trying to write business software in it. ergonomics matter
If I was to interpret that "strictly more powerful" statement, I would interpret it to be about how Racket's macro system works and what information its syntax objects carry. Or interpret it to mean the different languages it provides, like Typed Racket for example.
On the other hand I found using multiple cores much easier in GNU Guile.
Are they not both turing-complete?