Creating small decimal sometimes gives NaN

[Danvil]

Creating a small decimal when using u32 as type data sometimes gives NaN instead of 0.

Code:

pub type Dec = fraction::GenericDecimal<u32, u8>;
let d = Dec::from(0.0000000001);
println!("{d:?}");

Output:

GenericDecimal(NaN | prec=0; NaN; NaN)

Testing a bit more:

• Dec::from(0.000000001) => GenericDecimal(0.000000001 | prec=9; Rational(Plus, Ratio { numer: 1, denom: 1000000000 }); 0.000000001)
• Dec::from(0.0000000001); => GenericDecimal(NaN | prec=0; NaN; NaN)
• ...
• Dec::from(0.000000000000001); => GenericDecimal(NaN | prec=0; NaN; NaN)
• Dec::from(0.0000000000000001); => GenericDecimal(0 | prec=0; Rational(Plus, Ratio { numer: 0, denom: 1 }); 0)

Version: "0.15.3"

[dnsl48]

That is interesting, thank you for reporting this!
I believe the root cause for this may be undefined behaviour, since the u32 capacity is overflown.

[dnsl48]

NaN is currently used as the fallback value for when the memory capacity would be not enough to represent the value. Also, the from operation is infallible, so we don't really have any more meaningful options than return NaN when the values overflow.
Can you think of any better ways how we could handle that?