I like the explanation of how Rats solve a class of rounding errors, 0.3 - (0.2 + 0.1) equals exactly 0 for example. On the other hand, it's still a compromise that's shifting closer to correctness, fixing a bunch of potential bugs, but not all in that class:
Rakudo: > say 2 - (sqrt 2) ** 2 -4.44089209850063e-016 That's OK by me. I can also envision a type which can perfectly represent trigonometric and polynomial roots (backed by a symbolic math package?), that would solve this problem. I can see why that might be good in the core, for the same reasons that Rats are... or maybe put them in a module, along with non-integer exponents and trig functions, so if you can use functions with irrational numbers in their domain, you also get the numeric types that can perfectly represent them. -y
