How is it not? Both are serialization formats for trees with strings and numbers at the leaves.

Is there a serialization format you don't consider to be a bad re-invention of S-expressions?

Of course. There are many. Any binary format. Any ASN.1 format. DEF and LEF for hardware descriptions. The output of mysqldump.

Here's another example:

https://github.com/rongarret/tweetnacl/blob/master/ratchet.l...

starting at line 82. (That's one that I designed.)

>XML is absolutely S-expressions

You need a lot of predefined structure to capture attributes using brackets, much more than you do for dictionaries - which are just ordered pairs in a list when serialized.

(apologies, ninja deleted, I do not wish to continue this discussion)

There isn't a difference when it's serialized.