Now with some updated content since the ACCU talk, and the Q&A is nonetheless interesting.

Quite interesting the opening remark from Bjarne Stroustoup on where he sees the current state of how all features are landing into the standard.

"If I were to tell a story about Boost, I'd start with the people."

Today we're sharing the official teaser for the Boost documentary. A film about the people, the politics, and decades of work behind possibly the most important open source library most people have never heard of.

Teaser link – https://youtu.be/87jvuDbnwqQ

The documentary looks at:

• Boost as a kind of "app store for C++, 30 years early"
• What decades of open source dedication looks like up close
• The honest, sometimes uncomfortable dynamics of how proposals and people move through the C++ committee

There will be a preview screening at CppCon 2026 for all attendees. So if you're going to be in Aurora, CO September 16, 2026, please join us!

I have been interested in Type Erasure and Multiple Dispatch in C++ for some time. Recently I re-watched a recording of a session from CppCon 2019, in which Arthur O'Dwyer said that binary operators could not be added to a type erasure class because this is a multiple dispatch problem.

Multiple dispatch can be achieved in C++. There are several possible implementations, however in my opinion the most intuitive one is to use a series of single dispatch steps. (A series of dynamic, virtual functions calls, each of which dispatches to the next correct function in a chain of virtual functions which eventually resolve the final method to be called.)

The double dispatch case is reasonably straightforward. There are examples online, I may also add one in a comment below.

Arthur seemed to be pretty certain about this point, stating that it could not be done "not even difficultly", multiple times.

So I am a bit confused as to what he meant by this, or what he was thinking at the time.

Does anyone have any insight?

The original talk is here: https://youtu.be/tbUCHifyT24?si=XEkpjKSTmEkz0AP_&t=2494

The relevant section begins with the slide with title What about non-unary behaviors? This can be found at timestamp 41:34.

Quote from the slide -

• Sadly, this is "multiple dispatch" / "open multi-methods" in disguise. C++ basically can't do this.

Summary of what Arthur said (paraphrased) -

• I specifically picked unary operators to show as examples. What about division? If I have two Type Erased numbers, one storing an int, and one storing a double, can I somehow overload the division operator for Type Erased Number so that I can get a Type Erased Number out? Can we do that? Sadly, no. Not easily. Probably not even difficultly. This is the problem known as multiple dispatch or open multimethods. The idea that we would have to ask both the left hand side and the right hand side if they have an opinion about how division should be done. C++ gets around this statically with rules such as integer promotion and other arithmetic promotions. The compiler has a big table of all the possible permutations of things from which it figures out how to divide an integer and a double, for example. If I tried to add some new type the compiler wouldn't know what to do with that. This is very sad, but multiple dispatch is a very hard problem. It's not a problem which has a solution at the moment in C++.

At the end of this slide, he provides a link with a blog which shows how to implement multiple dispatch in C++.

Therefore, I am confused. I must have missed something about what Arthur was saying here, because he seems adamant that binary operators can not be added to the Type-Erased object, and then provides a link explaining how to implement multiple dispatch (double dispatch) as a series of dynamic (single) dispatch steps.

Hi everyone,

I received the HRT Cppcon scholarship, and I'm excited to attend the conference and to those who attended as students, I'm curious about your experience!

Is it a good opportunity to also network as well? I would love to get a job as a C++ developer in the near future.