Wrong result for e.g. √(2.25) - 1.5

[Wazhai]

Describe the bug

√(2.25) is 1.5 and the result shown is correct. However, subtracting 1.5 from that shows an incorrect result such as -2.1115953280960553738983525708397e-38.

This bug happens in all equivalent cases, e.g. with √(0.81) or any other square root that is a terminating decimal.

Steps To Reproduce

1. Use standard or scientific mode
2. Enter 2.25
3. Press √
4. Subtract 1.5
5. Result is wrong

Expected behavior

Result is 0

Device and Application Information (please complete the following information):

• OS Build: 10 0 17763 0
• Architecture: X64
• Application Version: 10.1812.10048.0

Additional info
Until recently, it also used to be that "√(4) - 2" didn't result in 0. It was fixed in the UWP app, but is a bug in calc.exe in older versions of Windows.

[HowardWolosky]

Relevant article: https://blogs.msdn.microsoft.com/oldnewthing/20040525-00/?p=39193

[luntik2012]

tl;dr
where is the fix?

[limingjie]

Multiple precision library should be used in calc.

[MicrosoftIssueBot]

This is your friendly Microsoft Issue Bot. I've seen this issue come in and have gone to tell a human about it.

[BerkhanBerkdemir]

Gnome's calculator Just Works™

[joshkoon]

@uhliksk Can you provide some details here on the fix you've proposed?

[uhliksk]

@uhliksk Can you provide some details here on the fix you've proposed?

There is already fix in code which is rounding result and calculating back inverted function to see if result of inverted funcion is same as input. If result is same as input then rounded value is used as result of function. Otherwise non-rounded result is used. This funcion is currently limited to round to integer numbers and thats why sqrt(4) is working well and sqrt(2.25) is not working. My solution is extension of actual fix to use up to 32 digits after decimal point instead of integers only.

[uhliksk]

@uhliksk Can you provide some details here on the fix you've proposed?

But I'm already preparing another pull request because I found another range of inputs where fix have to be little bit modified.