On 02/02/2019 10.15, Mattias Engdegård wrote:
> Thank you, that's an interesting idea! I don't think I'll work on it right now, but why don't you give it a go, using xr as the backend?

I've attached an implementation and screenshots.  rx seems to work nicely!

The expansion issue is indeed a bit of a problem.  It's also why I don't use rx often, in fact.
Another issue is regular expressions built with concat, since the parts they are made of are typically not 
The last issue is that the code I posted doesn't reveal the underlying expression (i.e. doesn't remove the display property) when the point is on it, which would be needed for a robust implementation.

By the way, could forms like "[A-Za-z]" be converted to a more compact representation? At the moment xr produces (any "A-Z" "a-z"), but it seems that (any "A-Za-z") would work as well and be shorter.

Again, nice work!
Clément.