Use RequireMsg or RequireMsgSym to improve error messages

[soronpo]

I took a brief look at your nice library that uses singleton-ops, and I recommend to use RequireMsg or RequireMsgSym to improve your error messages instead of the default implicitNotFound message.

[mandubian]

Thanks! I'll try!
This is a very draft version for now and I just wanted to prove it can work with singleton-ops & the concepts in the paper...
now I need to see how to improve things

[soronpo]

OK. I just wanted to help and mention this, since it might have been missed due to singleton-ops' lacking documentation (my fault).

[mandubian]

I confirm I had missed it ;)
I also was wondering: for now, it seems impossible to extend existing operators in singleton-ops externally to the lib, you must add it to the lib directly, am I right?

[soronpo]

Sadly you're right, and I don't see how can this be done otherwise. Fortunately, composition works flawlessly, so you should get most functionality from that. e.g.
type MyFunc[A,B,C] = A * B - math.Sqrt[C]

[mandubian]

Ideally, independently of singletons, I'd like to be able to write something like that with a bit of genericity:

def mult(m1: Dim2[A, B], m2: Dim2[B, C])(implicit r: Dim2[A, B] * Dim2[B, C] ===> Dim2[A, C]): Dim2[A, C]