Overall, I agree. Exceptions are messy and make it difficult to reason about code. That said, I think the macro at the bottom is even worse. I think a better solution to the one posted in the article is to use
std::expectedinstead. This gives you a typed union that allows you to return either a successful result or an error type.What's nice about it is that you don't need to add endless amounts of
if success {...} else {...}blocks. You can use the monadic operations (and_then,transform, etc.) to add your logic as normal while letting the compiler smoothly take care of doing the error checks. (In fact, I really wish golang has something similar to this, it would get rid of the endless error checking you have to write manually.)I wasn't able to find an example using
std::expected, and I tried writing one myself, but my version of g++ doesn't seem to support it yet. But here is a nicestd::optionalexample that should be pretty close to what you would do withstd::expected.The main problem with
std:: expectedis lack of language support. In theory, it works well as an alternative to exceptions, with nice self contained monadic statements. In practice, it is actually much worse than what the article suggests.main issues -
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as I said, no language level support. You eventually end up with messy code somewhere because the library code can't simplify things enough. You end up with if checks strew about that really oaught to be a language paradigm.
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there is not a lot of code making use of it, so at the boundaries of your code you have to make adaptations to and from
std:: expectedfrom whatever some library chose to use. -
adapting your existing codebase is basically impossible. Perhaps if you are starting a new project you can do it, but it is different enough that all your existing code must be updated to accommodate the new paradigm and it's just an awful experience doing the work and being in a mix of error handling.
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A construct that's not supported by g++ is not a superior alternative to a simple macro.
That said, once support is near-universal, it probably will be preferable.
Yeah, I meant to include that in my post but forgot. I actually started out thinking that it wouldn't be too hard to implement on top of
std::optionalbut then went down a rabbit hole to see if it already existing in the standard library.In any case, you could also always use abseil for features that haven't landed in the compiler yet. At work, I'm stuck on c++14, but having a great time using plenty of features from later versions thanks to abseil.
I tried coming up with a decent
Resulttype and Try macro in C++ and got nowhere. To be usable I need something like this:auto varname = Try(expression);Where the Try expression will either return the error type immediately or evaluate to the success type.
As far as I can tell there's no portable way to implement that macro in C++20, and nothing coming down the pipe either. I don't think chaining lambdas is good enough. It can make the code uglier than just manually checking returns.
I'll be happy if anyone can correct me though. The best I managed was still pretty gross:
TryBind(varname, expression);Works, but it just looks like a bad DSL at that point.
BOOST_OUTCOME_TRYXmay be what you're looking for. It's only available on gcc and clang though.Yeah, I came across that. I presume it just uses the GCC statement expressions extension under the hood.
No can do though, it has to work with MSVC too.