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C++20's concepts IMHO are a massive update over C++11. You can basically remove almost 90% of inheritance with them without incurring in any issue (you could do

C++20's concepts IMHO are a massive update over C++11. You can basically remove almost 90% of inheritance with them without incurring in any issue (you could do that earlier too, but at the expense of incredibly hard to read error messages - now that's basically solved thanks to concepts).

3836293648 2y ago
C++ concepts are a failure due to them only checking one side of the contract. And the other is basically impossible to implement without breaking other parts of the language
- gpderetta 2y ago
  concepts finally allowed retiring stupid SFINAE tricks. They are a huge success if only for that.
derriz 2y ago
I don't find the error messages produced by concepts much better than old school template errors. Maybe I got used to the latter with experience and definitely the compilers got better at generating useful error messages for templates as the years passed. On the other hand when I have to review code where a significant portion of the source relates to concepts, my heart sinks. In my opinion, C++ "concepts" are the least useful C++20 addition to the language - awful syntax, redundancy everywhere (multiple ways of writing the same thing). And for what? Potentially better error messages? Another gripe; of all the generic overloaded words available to describe this C++ feature, "concept" must be the least descriptive, least useful. Why pick such a meaningless name that does absolutely nothing to even suggest what the feature does?
- TuxSH 2y ago
  > In my opinion, C++ "concepts" are the least useful C++20 addition to the language - awful syntax, redundancy everywhere (multiple ways of writing the same thing). They're not the least useful C++20 addition, in fact they're amongst the most useful ones. In particular the addition of the "requires" expression is the real killer here. > And for what? Potentially better error messages? Removing even more enable_if and making template code even easier to read (you could do some of that with if constexpr + static_assert in C++17, but there were gotchas). Oh and it allows you to check for the presence of members in classes, which you couldn't do before.
- gpderetta 2y ago
  >[...] "concept" must be the least descriptive, least useful. Why pick such a meaningless name That's the name that Stepanov used 30 years ago to describe the informal type constraints of templates and has been in use in the community since them. Choosing anything else for the language feature would not make sense.

3836293648 2y ago

C++ concepts are a failure due to them only checking one side of the contract. And the other is basically impossible to implement without breaking other parts of the language

gpderetta 2y ago
concepts finally allowed retiring stupid SFINAE tricks. They are a huge success if only for that.

derriz 2y ago

I don't find the error messages produced by concepts much better than old school template errors. Maybe I got used to the latter with experience and definitely the compilers got better at generating useful error messages for templates as the years passed. On the other hand when I have to review code where a significant portion of the source relates to concepts, my heart sinks. In my opinion, C++ "concepts" are the least useful C++20 addition to the language - awful syntax, redundancy everywhere (multiple ways of writing the same thing). And for what? Potentially better error messages? Another gripe; of all the generic overloaded words available to describe this C++ feature, "concept" must be the least descriptive, least useful. Why pick such a meaningless name that does absolutely nothing to even suggest what the feature does?

TuxSH 2y ago
> In my opinion, C++ "concepts" are the least useful C++20 addition to the language - awful syntax, redundancy everywhere (multiple ways of writing the same thing). They're not the least useful C++20 addition, in fact they're amongst the most useful ones. In particular the addition of the "requires" expression is the real killer here. > And for what? Potentially better error messages? Removing even more enable_if and making template code even easier to read (you could do some of that with if constexpr + static_assert in C++17, but there were gotchas). Oh and it allows you to check for the presence of members in classes, which you couldn't do before.
gpderetta 2y ago
>[...] "concept" must be the least descriptive, least useful. Why pick such a meaningless name That's the name that Stepanov used 30 years ago to describe the informal type constraints of templates and has been in use in the community since them. Choosing anything else for the language feature would not make sense.