C++26: std::inplace_vector

[u/User_Deprecated]

https://www.sandordargo.com/blog/2026/08/26/cpp26-inplace-vector

[u/bartgrumbel]

I am sure there is a good reason for that, but why is the "optional reference" not simply a pointer? Is that not semantically the same thing, but way easier to deal with.

I.e. why

std::optional<T&>

and not simply

T*

[u/stilgarpl → u/bartgrumbel]

Optional is monadic, so it's much safer to deal with. You can call it like

inplace_vector.try_push_back(x).or_else(...);

[u/Ameisen → u/stilgarpl]

I won't lie - I prefer how C# would handle this: returning a bool and having an out parameter or such.

I find an actual if to be easier to read than .or_else(...)....

[u/WHY_DO_I_SHOUT → u/Ameisen]

Modern C# prefers returning an optional reference, FWIW...

[u/Ameisen → u/WHY_DO_I_SHOUT]

Yes, but Nullable semantics in C# are vastly nicer than std::optional in C++.

Including trivially using if with them:

if (Method() is {} value)

I should also point out that in C#, Foo? is identical to Foo if Foo is a reference-type. That would be the equivalent of std::optional<T&> being a type-alias for T*.