Your balance is $0.30000000004
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Your balance is $0.30000000004
1–10 of 69 posts
Re: Your balance is $0.30000000004
#2You would think that this is a fairly rookie error and that big companies would know better, but I regularly see this on Uber: https://i.imgur.com/qDACtG0.png
Re: Your balance is $0.30000000004
#3Good example of a leaky abstraction. JavaScript developers almost never have to worry about or completely understand the intricacies of floating-point arithmetic, until errors like this happen. https://en.wikipedia.org/wiki/Leaky_abstraction
Re: Your balance is $0.30000000004
#4You would think that this is a fairly rookie error and that big companies would know better, but I regularly see this on Uber: https://i.imgur.com/qDACtG0.png
On the surface one would think big companies should "know better". I mean, a large company is the accumulation of centuries or even millennia of career experience. Unfortunately, they also contain just as much accumulated nonsense and foolishness; and enough bureaucracy and organizational cruft to hide it forever.
Re: Your balance is $0.30000000004
#5Good example of a leaky abstraction. JavaScript developers almost never have to worry about or completely understand the intricacies of floating-point arithmetic, until errors like this happen. https://en.wikipedia.org/wiki/Leaky_abstraction
I wouldn’t consider this a leaky abstraction.
Floating point numbers are explicitly not trying to be an abstraction for real numbers, but rather an approximation for them that is good enough for most purposes (if you’re careful in how you use them).
That they might not be taught as such is another problem.
Re: Your balance is $0.30000000004
#6Martin Fowler's money pattern [0] solves this problem. Just make sure whenever you're dealing with currencies to use a value object for money, rather than float. Lots of languages have libraries for this pattern. [1]
Re: Your balance is $0.30000000004
#7Work with cents everywhere and format the output in the UI. Done.
Re: Your balance is $0.30000000004
#8You would think that this is a fairly rookie error and that big companies would know better, but I regularly see this on Uber: https://i.imgur.com/qDACtG0.png
browser console:
(1.005).toFixed(2)
(1.005).toFixed(20) reveals the problem.
Math.round(1.005 * 100) // wrong
In the end these conversion errors are not solvable in any language, so you have to "cut off" somewhere. There are different approaches to this.
Wasn't there a case where programmers stole the "wrong" cent and wasn't The Office a persiflage on that?
Re: Your balance is $0.30000000004
#9Good example of a leaky abstraction. JavaScript developers almost never have to worry about or completely understand the intricacies of floating-point arithmetic, until errors like this happen. https://en.wikipedia.org/wiki/Leaky_abstraction
This is not a leaky abstraction. JavaScript doesn't pretend that the numeric type is anything other than an IEEE-754 float. It would be a leaky abstraction if JavaScript said "this type can represent all real numbers!" but that would be insanity.
Re: Your balance is $0.30000000004
#10You would think that this is a fairly rookie error and that big companies would know better, but I regularly see this on Uber: https://i.imgur.com/qDACtG0.png
browser console: (1.005).toFixed(2) (1.005).toFixed(20) reveals the problem. Math.round(1.005 * 100) // wrong In the end these conversion errors are not solvable in any language, so you have to "cut off" somewhere. There are different approaches to this. Wasn't there a case where programmers stole the "wrong" cent and wasn't The Office a persiflage on that?
That was the main plot of Office Space.