I love the syntax for checked math. a + b for wrap around, a +? b to raise an exception on under/overflow, and a +~ b for maximum performance, leaving behavior on under/overflow undefined (including floats having undefined behavior on +-Inf and NaN).

Compared to e.g. Rust (one of the better modern examples of easy rigorous math) I really like how concise they are. What I'm missing are saturating operations. I know some people find them useless, and through a "perfect results" lens they are, but they still give you the closest representable number. And they are often intuitive for humans since that's how most analog instruments work

It's interesting that Rust and Pony have différent default for addition.