[shhsshs]

> If your language has bad defaults, you may have to ask for the right rounding mode explicitly.

Is the author implying Rust's default rounding behavior is a bad default? In what world is "ties to even" a GOOD default?

[wizerno]

It's also called banker's rounding. To understand why it's a good default, you can check out https://mathematica.stackexchange.com/a/2120

[alkonaut]

The motivation for the seemingly strange rounding is that a set of numbers can be rounded before summing without biasing the sum. It has good use cases but so do all rounding modes.

[tavianator]

In general, if some recommendation from IEEE 754 (the floating-point standard) seems strange, its because someone like William Kahan thought about it in great detail and you'd be wise to follow it.

https://en.wikipedia.org/wiki/Rounding#Rounding_half_to_even