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The optional header is in sync with the specification of std::optional. Certain test cases have been added for detecting ambiguous conversions that optional should resolve. These ambiguities were introduced when converting from if else constructs to the ternary ? : operator, as that has rules for calculating a common type, where if / else does not.

  • initialization of value_ is via utility function
  • value_or supports braced initialization
  • value_or decays the copy it makes, removing cv qualifiers
  • borrowed range flag is in a more direct style
  • value_ is initialized to nullptr, the nullopt constructor delegates, and other constructors no longer branch

Paper is post LWG review and is immutable at P2988R12.

steve-downey and others added 30 commits March 9, 2025 14:21
Use convert-ref-init-val to convert a U to a T& and initialize value with its
address.
GCC 15 correctly notes that 0xCAFEBABE is an unsigned int as an auto.
LEWG had several suggestions for wording.
Use conditional operator instead of if else.
- [X]  in p7 what is U? There is something missing
- [X]  it should be invoke_result_t<F>
- [X]  the definition of U should be consistent
- [X]  in p4: we shouldn’t use trailing return types here
Now that "contains a value" is defined for reference optionals.
steve-downey and others added 22 commits March 26, 2025 14:18
Update code, also
Add delegation for optional(nullopt_t) constructor.
Tref gets lost.
Fix include/beman/optional/optional.hpp:1368: optioanl ==> optional
Pin one side of value_or ternary to prevent ambiguity in conversions.
Should be "models invocable" not "models invocable<>"
1.  missing expos italization of val in contained value defn for optional<T&>

2. In iterator begin() since contained value is now a reference, change the
iterator referring to to be to *val

3. Add mandates for transform to require that the result of invoking the
supplied function to the contained value can create an object.
@steve-downey steve-downey requested review from camio, neatudarius and a team as code owners April 4, 2025 22:18
@steve-downey steve-downey requested a review from RaduNichita April 4, 2025 22:18
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coveralls commented Apr 4, 2025

Pull Request Test Coverage Report for Build 14283564092

Details

  • 18 of 18 (100.0%) changed or added relevant lines in 1 file are covered.
  • No unchanged relevant lines lost coverage.
  • Overall coverage increased (+2.0%) to 96.82%

Totals Coverage Status
Change from base Build 14282085635: 2.0%
Covered Lines: 274
Relevant Lines: 283

💛 - Coveralls

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@neatudarius neatudarius left a comment

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LGTM and good job!

PS Didn't review content under papers/.

// Example from P2988R5: optional reference.
[[maybe_unused]] Cat* old_cat = std17::api();
[[maybe_unused]] beman::optional::optional<Cat&> new_cat = std26::api();

return 0;
}

struct derived;
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Thanks for splitting this!

@neatudarius
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Should we merge this?

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3 participants