This is a response to the other thread. I would have written
it there but I just subscribed.

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> What about printing underscores in the REPL though? I thought that would
> be the main thing that's useful. A typical example would be using the
> Scheme REPL as a fancy calculator. It's not as critical (and can often
> be unwanted) to have underscores when printing S-expressions to files.

Don't we already have the `display'/`write' distinction for
this? So that display could print numbers with underscores,
and write would give "plain" numbers?
--
hugo