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Reflection for C++26

(isocpp.org)
196 points svlasov | 1 comments | 30 Jun 24 11:26 UTC | HN request time: 0.336s | source
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Dwedit ◴[01 Jul 24 22:04 UTC] No.40851285[source]▶
Compile time or runtime? Compile time reflection would be completely painless and bloat-free.
replies(3): >>40851300 #>>40851330 #>>40851736 #
shortrounddev2 ◴[01 Jul 24 22:08 UTC] No.40851330[source]▶
RTTI is a super vital feature for deserializing without having to generate code or write a ton of tedious boilerplate. I'd be very happy with RTTI in C++ and my life would be instantly easier if there were RTTI in typescript so I didn't have to use any of the hacky solutions out there for deserializing JSON on backends without RTTI.

I suppose C++'s template system might be able to generate JSON deserializers with static reflection as well

replies(2): >>40851369 #>>40851644 #
chongli ◴[01 Jul 24 22:13 UTC] No.40851369[source]▶
You don't need RTTI to deserialize data in a clean way. What you need is return-type polymorphism. Haskell has this and it makes writing serializers and deserializers symmetric and totally painless.
replies(1): >>40851442 #
fooker ◴[01 Jul 24 22:20 UTC] No.40851442[source]▶
Return type polymorphism and inheritance doesn't mix very well.

Swift got into this mess early in it's lifecycle and it's type checking is still more expensive than the rest of the compiler combined, and unpredictable on top of that.

replies(2): >>40851982 #>>40852119 #
Maxatar ◴[01 Jul 24 23:53 UTC] No.40852119[source]▶
C++ has both return type polymorphism and inheritance. What it doesn't have is the kind of type inference that Haskell has. Its type inference is very limited.
replies(1): >>40853546 #
fooker ◴[02 Jul 24 04:22 UTC] No.40853546[source]▶
You can't have two functions that differ in just the return type in C++
replies(3): >>40853661 #>>40853704 #>>40857429 #
1. Maxatar ◴[02 Jul 24 15:12 UTC] No.40857429[source]▶
You certainly can and I know there are several JSON libraries that do it. The gist of it is to write a struct and overload the conversion operator for the set of return types you want to support, for example overload the conversion operator to int and std::string. As soon as the instance of that struct is used in a context that needs an std::string, then it calls the string overload.