## Summary of the Pull Request
This PR continues the tradition of alphabetical progress. After
[MBGA](#41961), we move on to **MCBA — Make Calculator Better Again!**
- Introduces limited automatic correction and completion of expressions.
- The goal is to allow uninterrupted typing and avoid disruptions when a
partially entered expression is temporarily invalid (which previously
caused the result to be replaced by an error message or hidden by the
fallback).
- The implementation intentionally aims for a sweet spot:
- Ignores trailing binary operators.
- Automatically closes all opened parentheses.
- It is not exhaustive; for example, incomplete constants or functions
may still result in an invalid query.
- Copy current result to the search bar.
- Adds an option to copy the current result to the search bar when the
user types `=` at the end of the expression.
- Adds a new menu item for the same action.
- Fixes the **Save** command to also copy the result to the query.
- Adds support for the `factorial(x)` function and the `x!` expression.
- Factorial calculations are supported up to `170!` (limited by
`double`), but display is constrained by decimal conversion and allows
direct display of results up to `20!`.
- Adds support for the `sign(x)` function.
- Adds support for the `π` symbol as an alternative to the `pi`
constant.
- Adds a context menu item to the result list item and fallback that
displays the octal representation of the result.
- Implements beautification of the query:
- Converts technical symbols such as `*` or `/` to `×` or `÷`,
respectively.
- Not enabled for fallbacks for now, since the item text should match
the query to keep the score intact.
- Implements additional normalization of symbols in the query:
- Percent: `％`, `%`, `﹪`
- Minus: `−`, `-`, `–`, `—`
- Factorial: `！`, `!`
- Multiplication: `*`, `×`, `∗`, `·`, `⋅`, `✕`, `✖`, `\u2062` (invisible
times)
- Division: `/`, `÷`, `➗`, `:`
- Allows use of `²` and `³` as alternatives to `^2` and `^3`.
- Updates the unit test that was culture sensitive to force en-US output
(not an actual fix, but at least it clears false positive for now)
- Fixes pre-parsing of scientific notation to prevent capturing minus
sign as part of it.
- Fixes normalization/rounding of the result, so it can display small
values (the current solution turned it into a string with scientific
notation and couldn't parse it back).
- Updates test with new cases
## Pictures? Moving!
Previous behavior:
https://github.com/user-attachments/assets/ebcdcd85-797a-44f9-a8b1-a0f2f33c6b42
New behavior:
https://github.com/user-attachments/assets/5bd94663-a0d0-4d7d-8032-1030e79926c3
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist
- [x] Closes: #43481
- [x] Closes: #43460
- [x] Closes: #42078
- [x] Closes: #41839
- [x] Closes: #39659
- [x] Closes: #40502
- [x] Related to: #41715
<!-- - [ ] Closes: #yyy (add separate lines for additional resolved
issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [x] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx
<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
<!-- Enter a brief description/summary of your PR here. What does it
fix/what does it change/how was it tested (even manually, if necessary)?
-->
## Summary of the Pull Request
1. Remove some AI generated nonsense case
2. Add ISettingsInterface for those ext for testing purpose.
3. Add query test.
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist
- [x] Closes: #40897
- [x] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [x] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx
<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
---------
Co-authored-by: Yu Leng <yuleng@microsoft.com>
