Lambda the Ultimate

I think this may have been mentioned before on LTU, but I thought I would post the link again as I found this series of lectures by Jürgen Giesl great for learning Haskell.

The lectures are 2005-SS-FP.V01 through 2005-SS-FP.V26.

Videos 2005-SS-FP.U01 through 2005-SS-FP.U11 are exercise answer sessions, so you probably don't want those.

They are given in english.

The Unimperative language I posted about nearly a year ago has been reborn as a "concatenative" language, ala Joy. ( personally I would prefer to call it a compositional language, but who am I to buck trends ).

The Unimperative language is also a tiny subset of C++, so I am trying to decide on the concatenation operators. Currently I support separate left-concatenation (f << g == f . g) and right-concatenation (g >> f == f . g). In the end this gets a bit clumsy, and I find hard to read. So I want to overload the comma operator.

My question is this: which concatenative form (left or right) should the comma overload to? In other words should I treat it as a left to right sequencing operator, or as a composition operator?