Atomics: If of length 0 or 1, they are basically printed as they are.
Numerics are formated with num.format.
If of length greater than 1, they are collapsed witd “,” and clipped.
so they do not become excessively long.
Expressions will be converted to plain text.
All others: Currently, only their class is simply printed
like “<data.frame>”.
Lists: The mechanism above is applied (non-recursively) to their elements.
The result looks like this:
“a=1, <unamed>=2, b=<data.frame>, c=<list>”.