> For what it is worth, it would be valid Common Lisp "potential number",
> so in Common Lisp it would not conflict with a symbol.
>
> https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node189.html

Yeah. "Potential number" is an awesome technical term :) From the
glossary: "A textual notation that might be parsed by the Lisp reader in
some conforming implementation as a number but is not required to be
parsed as a number. No object is a potential number---either an object
is a number or it is not."

They write pi like this: 3.141_592_653_589_793_238_4

And there's a lot more weird stuff that we probably don't want :D Things
like -3.7+2.6i-6.17j+19.6k

What's your opinion of having this in Kawa, or do you perhaps have it
already?