@Scot Gould I do not know how to thank you, you are very kind! In my youth at university I did had a course in computer science that included programming, in BASIC - i am talking eons ago! However our professor was really fond of "block diagrams", that was writing down the process (the logic of the argument if you will), then you "only" needed to translate in a programming language. This was late 80s, and now it is all object based, which I am not even sure I know what it means. I am a theorist, and only use Maple for quick checks of counterexamples and quick computations.

You are indeed right, I was using 1D input, and now I know what it means. I am trying to prove the invertibility of a matri with a particular structure, and being stuck, I was hoping that by visualising an example in Maple might provide some inspiration - so I have taken a minimalist approach to trying to get to the bare minimum of Maple "proficiency" to get to see that matrix, and I am fully aware that the full worksheet is a hair raiser of computational inefficiency :-)

But this episode proves to me that I really need to brush up and take myself into the 21st century, rather than staying a dinosaur! So your document is most helpful!

Again, many thanks for your generosity and your time!

@Scot Gould forgive me but it will take me some time to understand what you write, as I am an absolute beginner (started studing programming in Maple the whole of 36 hours ago!). But I'll look it up. Thank you.

@Scot Gould thank you , will do!

@Carl Love thank you ever so much, you are a star! It works now! 

I have Maple 2023 for Mac, maybe the mac version is different? Unless we are already at Maple 2024 and I am lagging behind.

Anyhow, very many thanks!

@Carl Love first and foremost, thanks a million! I have to understand the first solution, but the second makes immediate sense to me.

however, running both of them returns an error message. For the second one I get an "Error, invalid sequence", though I cannot see why it is throwing up this error, since I can't see anything missing (I tried adding ";" after "end do", but that does not seem to be the problem.

The first solution instead returns the error "Error, invalid arrow procedure".

I am going to abuse your patience and ask if you see anything obvious in why I get these errors? Many thanks!