Parse double precision using InvariantCulture

[stephenquan]

Description of Change

Parse a double using InvariantCulture to avoid issues when CurrentCulture changes, such as to 'ar-AR'.

Linked Issues

• Fixes [BUG] MathExpressionConverter doesn't support negative numbers when in Arabic (ar_AR) #2721
• Fixes [BUG] MathExpressionConverter not working correctly on ios for version 11.0.0 or higher #2665

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (omitted, since this is a minor change)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: (no change)

Additional information

None

[MartyIX]

It might be good to turn on the CA1305 analyzer in the project to avoid similar bugs.

[stephenquan]

@MartyIX based on your feedback, I applied the CA1305 analyzer and found multiple conversions in MathExpression.shared.cs that needed updates to satisfy the analyzer. After the changes all unit tests for the math converters still passed.

The CA1305 analyzer also picked up new issues which isn't part of the scope of this PR. Would you like me to create split 3 issues to look? (Camera CA1305, SpeechToText CA1305, Badge CA1305)?

F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)
F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)
F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)
F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)
F:\Maui\src\CommunityToolkit.Maui.Camera\CameraInfo.shared.cs(99,4): error CA1305: The behavior of 'StringBuilder.Append(ref StringBuilder.AppendInterpolatedStringHandler)' could vary based on the current user's locale settings. Replace this call in 'CameraInfo.ToString()' with a call to 'StringBuilder.Append(IFormatProvider, ref StringBuilder.AppendInterpolatedStringHandler)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)
F:\Maui\src\CommunityToolkit.Maui.Core\Essentials\SpeechToText\OfflineSpeechToTextImplementation.android.cs(188,56): error CA1305: The behavior of 'int.ToString()' could vary based on the current user's locale settings. Replace this call in 'RecognitionSupportCallback.OnError(int)' with a call to 'int.ToString(IFormatProvider)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)
F:\Maui\src\CommunityToolkit.Maui.Core\Essentials\Badge\BadgeImplementation.windows.cs(22,40): error CA1305: The behavior of 'uint.ToString()' could vary based on the current user's locale settings. Replace this call in 'BadgeImplementation.SetCount(uint)' with a call to 'uint.ToString(IFormatProvider)'. (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1305)

Build failed with 7 error(s) and 81 warning(s) in 3.8s

[MartyIX]

I'm in no position to say what you should do or not, I'm just a random passerby :)) However, I believe it would be a nice new PR or PRs¹ to avoid cramming this PR.

Footnotes

1. If the number of necessary changes is small, then probably just one PR. ↩

[stephenquan]

@MartyIX, as per your feedback, I have created a new split issue #2744 to avoid cramming this PR.

[VladislavAntonyuk]

You can change the pattern to something like this:

@"^-?\d+[.,]?\d*$"

It should match:

• 123
• -123.45
• -123,45

[stephenquan]

Hi @VladislavAntonyuk, sorry it's been awhile since I've replied to your comment. The struggle I have with your suggestion is that we're trying to make the expressions follow InvariantCulture so that the expressions are deterministic and will not be influence by language changes. The other reason is that the comma (,) is already part of the expression for delimiting functional arguments (e.g. atan2).

[stephenquan]

Hi @VladislavAntonyuk, I watched this month's standup and noted two key discussions:

• Whether developers can pass CultureInfo as a parameter as a new parameter to the MathExpressionConvertre/MultiMathExpressionConverter
• Whether the CultureInfo parameter passed to IValueConverter/IMultiValueConverter convert methods can be used (which, from my limited understanding/testing, seems to follow whatever CultureInfo.CurrentUICulture is set to)

Just to reiterate my application's use case: the application supports runtime switching between 30+ languages, which updates CultureInfo.CurrentCulture and CultureInfo.CurrentUICulture. However, our UI uses MultiMathExpressionConverter for some spinner logic (e.g., x0 ? -90 : 0) which needs to be language agnostic. In Arabic, parsing the negative sign causes a crash. The crash can be understood because of Arabic not recognizing the minus sign.

CultureInfo.CurrentCulture = new CultureInfo("ar-AR");
var value = double.Parse("-90"); // Throws System.FormatException: 'The input string '-90' was not in a correct format.'

In our application, we have worked around this problem by coming up with alternates ways to specify -90.

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[stephenquan]

@VladislavAntonyuk I've pushed a new commit that introduces the Culture property for both MathExpressionConverter and MultiMathExpressionConverter. Ideally, this should remain set to the default InvariantCulture. That said, I've tested it with several European cultures - such as "fr-FR", which uses a comma as the decimal separator - and it performs as expected.

The original issue, however, supporting Arabic as the numeric culture, is currently out of scope. Properly handling Arabic number formatting would require a significantly more robust parsing strategy to accommodate all relevant symbols. The example below highlights the mapping we need to consider to convert Arabic number format to Western number format (including swapping the decimal with the comma).

🧮 Arabic Number Formatting Summary (Culture: ar-SA)

Component	Arabic Format	Unicode	Notes
Digits	Arabic-Indic (٠١٢٣٤٥٦٧٨٩)	U+0660–U+0669	Replaces Western digits (0–9)
Decimal Separator	Arabic decimal ٫	U+066B	Replaces the Western .
Thousands Separator	Arabic comma ٬	U+066C	Replaces the Western ,
Minus Sign	Unicode minus −	U+2212	Replaces the Western Hyphen-minus -

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[stephenquan]

Adding #2665