ILanguage

I also quite liked that idea. It would probably be a nightmare to actually use, but it's definitely a creative solution to dealing with infix operator precedence. The only implemented language I know of with this feature is the obscure array lang I (an incrementation of the J language's name I assume) by Marshall Lochbaum: https://github.com/mlochbaum/ILanguage

It does have : for assignment, although there's no scoping, and you have to assign to symbols that are surrounded in single quotes. You can see some examples at https://github.com/mlochbaum/ILanguage/blob/master/examples/... . They need extra parens, since : is an ordinary function and has the symbol on the left. Your overall point is right; I didn't really try to address any issues with assignment. And of course there are lots of things to try, and I hope some of them make it into some other language I design!

For left-to-right execution, the dissonance between execution and statement separators (including functions and list notation) is very bad as you note.[0] For right-to-left execution, assignment has a similar problem: the name really needs to be on the left to allow easily scanning definitions, but this conflicts with the evaluation order. Particularly statements with multiple assignments in them don't work at all. Right-to-left is usually framed as a more "declarative" or "functional" style (and note that application and composition of mathematical functions follows this order) while left-to-right is considered "imperative". In my first major language, I,[1] I did change to a left-to-right order. For BQN, which is intended to stick much closer to traditional APL, I didn't want to make such a large break from the methods that have worked