C++ was so much cleaner in the 90s, when it was still essentially "C with classes," which is how I like to use the language. Modern standards have turned it into an ugly mess.
Amen. The syntax just kept getting more and more complicated. I gave up in the late 1990s. Ironically for this post, I now prefer to write everything in Clojure. It seems like my own journey has paralleled Rich’s journey. Maybe that’s why I appreciate so many of the design choices in Clojure. It’s not perfect, but it’s really, really good.
And then they introduced coke at committee meetings, the crazy shit they've been coming up with lately shows absolutely zero understanding of the complexity issue.
I also use C++ as "C with classes," however I will concede that many of the modern C++ additions, particularly around templating, are extremely convenient. If you haven't had a chance to use requires, concepts, "using" aliases, etc I'd recommend giving them a try. I don't reach for those tools often, but when I do, they're way nicer than whatever this article is demonstrating from 1994! Oh yeah, also lambdas, those are awesome.
I dunno, I skimmed the article's 31 year old code examples and immediately thought they would be shorter and simpler in c++11 or later.
But it's important to see the 1994 (and 1998) view of the world to understand how modern c++ features work. Because they start from that worldview and start adding convenient stuff. If you don't understand how c++ used to work, you may be confused with why c++ lambdas look so weird.
This is a thing C++ advocates say that tells me they’ve never really tried to do it and share that codebase with others or integrate with other codebases.
You generally don’t get to pick what parts other people want to use, which means that in the end you still have to deal with the entirety of the language.
not sure why the title was renamed, but i thought this was interesting primarily because it's the early work of Rich Hickey, famous for making the Clojure language.
Doing this today I'd just have a std::function parameter and have callers pass in a lambda. I may use a third party std::function that doesn't have the weird copy semantics though
> I may use a third party std::function that doesn't have the weird copy semantics though
Note that C++23 brings std::move_only_function if you're storing a callback for later use, as well as std::function_ref if you don't need lifetime extension.
Can you elaborate on your third point? What would a class need to do to affect debugging info?
Regarding your fourth point, sometimes an architecture can be vastly simplified if the source of information can abstracted away. For example, invoking a callback from a TCP client, batch replay service, unit test, etc. Sometimes object oriented design gets in the way.
To your first point, I think RAII and architecture primarily address this. I'm not sure that I see callback implementation driving this. Although I have seen cancellable callbacks, allowing the receiver to safely cancel a callback when it goes away.
>> Can you elaborate on your third point? What would a class need to do to affect debugging info?
Common implementations are a function pointer + void* pair, which in most debuggers just show you two opaque addresses. Better to include a info block -- at least in debug builds -- with polymorphic type pointers that can actually deduce the type and show you all the fields of the receiver.
>> sometimes an architecture can be vastly simplified if the source of information can abstracted away.
"sometimes" is doing a lot of heavy lifting here. That's my whole point -- more often than not I see some type of homespun functor used in cases that are _not_ simplified, but actually complicated by the unnecessary "plumbing."
>> RAII and architecture primarily address this
If the receiver uses RAII to clean up the callback, then you've reintroduced the "type-intrusiveness" that functors are meant to avoid...?
The only "standard" in 1994 was the C++ARM book (filled a similar role to the K&R C book) that served as basis for the ongoing standardization process, to be done in 1998.
[0] https://youtu.be/wo84LFzx5nI?si=SBv1UqgtKJ1BH3Cw&t=5159
It shows that C++ was considered too complex already in the 90s.
But it's important to see the 1994 (and 1998) view of the world to understand how modern c++ features work. Because they start from that worldview and start adding convenient stuff. If you don't understand how c++ used to work, you may be confused with why c++ lambdas look so weird.
That may be the case, but there are plenty of examples of elegant implementations.
JUCE, for instance:
.. I think that's kind of clean and readable, but ymmv, I guess?You generally don’t get to pick what parts other people want to use, which means that in the end you still have to deal with the entirety of the language.
Callbacks in C++ using template functors (1994) - https://news.ycombinator.com/item?id=18650902 - Dec 2018 (50 comments)
Callbacks in C++ using template functors – Rich Hickey (1994) - https://news.ycombinator.com/item?id=12401400 - Aug 2016 (1 comment)
Callbacks in C++ using template functors (1994) - https://news.ycombinator.com/item?id=10410864 - Oct 2015 (2 comments)
Note that C++23 brings std::move_only_function if you're storing a callback for later use, as well as std::function_ref if you don't need lifetime extension.
https://en.cppreference.com/w/cpp/utility/functional/move_on...
(i) Have they thought about the relative lifetimes of the sender and receiver?
(ii) Is the callback a "critical section" where certain side-effects have undefined behavior?
(iii) Does the functors store debugging info that .natvis can use?
(iv) Is it reeeeeeeally that bad to just implement an interface?
Even if it's 1994???
Regarding your fourth point, sometimes an architecture can be vastly simplified if the source of information can abstracted away. For example, invoking a callback from a TCP client, batch replay service, unit test, etc. Sometimes object oriented design gets in the way.
To your first point, I think RAII and architecture primarily address this. I'm not sure that I see callback implementation driving this. Although I have seen cancellable callbacks, allowing the receiver to safely cancel a callback when it goes away.
Common implementations are a function pointer + void* pair, which in most debuggers just show you two opaque addresses. Better to include a info block -- at least in debug builds -- with polymorphic type pointers that can actually deduce the type and show you all the fields of the receiver.
>> sometimes an architecture can be vastly simplified if the source of information can abstracted away.
"sometimes" is doing a lot of heavy lifting here. That's my whole point -- more often than not I see some type of homespun functor used in cases that are _not_ simplified, but actually complicated by the unnecessary "plumbing."
>> RAII and architecture primarily address this
If the receiver uses RAII to clean up the callback, then you've reintroduced the "type-intrusiveness" that functors are meant to avoid...?