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Title
t

Tristan Caron

01/17/2019, 7:57 PM
I use Kotlin
1.3.11
c

Czar

01/17/2019, 8:06 PM
1) Please use threads or edit original message when describing same issue. 2) Double is not suited for financial calculations, you cannot get precise numbers. See this answer here: https://stackoverflow.com/a/3730249/663012
t

Tristan Caron

01/17/2019, 8:18 PM
1/ I apologise for that; 2/ It looks interesting, thank you. Somehow it reminded me something about fixed point.
I changed everything into
BigDecimal
but the result is still the same.
c

Czar

01/17/2019, 8:31 PM
can you post a piece of code I can run to reproduce?
Unless whole JVM is horribly broken it should work 🙂
Note, I intentionally used your approach to make my code similar to yours, usually with BigDecimals you would write something like:
val totalHt = items.fold(BigDecimal.ZERO, BigDecimal::add)
t

Tristan Caron

01/17/2019, 8:42 PM
Yes, exactly. Even the number are not correct. It should not be
4296.5999999999
but
4296.6
because I only have 1 item with
price = 0.6
and
quantity = 7161
Thanks for the tip, I use BigDecimal.ZERO 🙂
c

Czar

01/17/2019, 8:43 PM
unless you start with a
Double
what you are describing should be impossible
I mean you're probably initializing
BigDecimal
with a
Double
, check this screenshot
t

Tristan Caron

01/17/2019, 8:51 PM
This what's happening. I can't even use breakpoints correctly. You may have found something. But when I use my rounding function, it should work no?
c

Czar

01/17/2019, 8:54 PM
No, it should not, there is no way for a double to represent something like a mathematical
0.6
precisely.
the nice rounded numbers you see during debugging is just eye candy.
Using floats or doubles for finance is like a mortal sin for a developer 😄 These types just are not designed to work like we need them to for financial stuff, for some other stuff too if you believe the military anecdote in this article: https://dzone.com/articles/never-use-float-and-double-for-monetary-calculatio
And here's more in-depth information from Oracle: https://blogs.oracle.com/corejavatechtips/the-need-for-bigdecimal (linked from the dzone article above)
t

Tristan Caron

01/17/2019, 9:01 PM
Well I am lucky that it's not prod yet 😄 I am getting the value from a mongodb collection, and the values are numbers. That might be why my BigDecimal are acting like this.
Thanks a lot for you help. I think I have my solution.
👍 1
c

Czar

01/17/2019, 9:09 PM
Yeah, with MongoDB you must use strings, it does not have dedicated decimal type beyond float/double
I don't know what you're using for mapping, but e.g. Spring Data MongoDB supports Java/Kotlin
BigDecimal
<-> BSON
String
mapping
Oh, actually it seems MongoDB 3.4 did add a suitable decimal type: https://docs.mongodb.com/manual/tutorial/model-monetary-data/#numeric-decimal Check if your mapper supports it, or use strings.
👍 1
t

Tristan Caron

01/17/2019, 11:07 PM
By the way, how did you do to display the values on the side (from your screenshot)
s

Shawn

01/17/2019, 11:23 PM
That looks like maybe the output of a scratch file run in worksheet mode (i.e. using the big play button in the top left of the scratch editor)
👍 1
t

Tristan Caron

01/17/2019, 11:25 PM
Well I converted everything into Decimals, it still not working... Even this dirty code like
val totalTtc = decimalFormat.format((totalHt + (totalHt / 100) * invoice.taxPercent).toString().let {
                it.substring(0, it.indexOf(".") + 4)
            })
I am becoming crazy... I've added logging, they do not appear. I raised an exception in the middle of my code, to make crash my app on purpose, nothing happen, it's just continuing like if it was not there.
s

Shawn

01/17/2019, 11:48 PM
Are you rebuilding and actually running the newly built code?
t

Tristan Caron

01/17/2019, 11:49 PM
When I do changes and click on the little bug, is it not supposed to rebuild?
s

Shawn

01/17/2019, 11:52 PM
Ahh I think I know what’s happening
hitting the button is launching a new debug session and you might be still interacting with an old one
t

Tristan Caron

01/17/2019, 11:53 PM
Yep, you are right, I ran it using the terminal and it's now working 🙂
s

Shawn

01/17/2019, 11:54 PM
What version of IntelliJ are you running?
t

Tristan Caron

01/17/2019, 11:54 PM
2018.3.2
s

Shawn

01/17/2019, 11:54 PM
they changed the default behavior from allowing sessions to run in parallel to disallowing that
oh huh
you might want to check in the run configuration to see if “Allow running in parallel” is enabled? Do you get a warning when you try to restart a debugging session?
t

Tristan Caron

01/17/2019, 11:58 PM
It is not enabled