Store bills in rational cents rather than floats

[Natim]

Storing bills as floats leads to a number of problematic edge cases.

Instead we should handle money as integers in cents and then display them as float in the end.

We did this change on the elm-ihatemoney project during yesterday hackathon with @gdeest and I think we should fix it in the API as well.

[Natim]

Refs spiral-project/elm-ihatemoney#16

[almet]

I believe this is a duplicate of #165, isn't it?

[Natim]

Yes but #165 was closed while we are still using float. And as you well know, we have a couple more bugs with the external lib too.

[Natim]

More interesting research here: https://ren.zone/articles/safe-money

[almet]

Yes, you're right : we should move away from these silly floats!

[LeoMouyna]

Hey @Natim !
Are you sure you want to store integers ? After reading your article we might want to store it as decimal string: https://docs.python.org/3/library/decimal.html and do operations with fractions: https://docs.python.org/3/library/fractions.html
What do you think about this ?

[Natim]

Yes you are exactly right.

[rom1dep]

@LeoMouyna how do you plan on serializing Fraction('1.1') + Fraction('0.3') + Fraction(100 ,3)? as a (521, 15) tuple?