A quick note if you're migrating old code to the new version: the "parameter" macro is gone. Use an ordinary variable and "w/" instead. In other words, rather than doing this:
(parameter foo ...)
(w/foo ...)
Do this:
(= foo ...)
(w/ foo ...)
Also, "=" still works like it does in Arc, but I recommend using "var" rather than "=", because it's hyper-static:
(var foo ...)
(w/ foo ...)
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Another difference is that keyword arguments are no longer supported at all. This is because it's quite difficult to implement them properly, only a single function in Arc/Nu actually used them, and they're not backwards compatible with Arc 3.1, so I decided it wasn't worth it.
If you run into any other difficulties, feel free to post here and we can work it out.
Why didn't I just include it in Arc/Nu? Because I think the new system is better, so in the long run I really do want people to switch to the new system.