Cost of enum-to-string: C++26 reflection vs. the old ways

6 comments

• randusername 11 minutes ago
  I can't imagine myself using reflection much, but maybe it will eliminate a lot of feature proposals bogging down the committee and they can focus on harder problems.

  It would be cool if the stated goal of C++29 was compile times.
• w4rh4wk5 1 hour ago
  I've been wondering about debug-ability of code using reflection. X-Macros are quite annoying to step through in most debuggers, though possible. While the code in the first example is evaluated fully at compile-time, how would you approach debugging it?
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  • cenamus 7 minutes ago
    I mean it's still C++ that's compiled and executed, surely the compiler would be able to provide a way to hook into that?
• HarHarVeryFunny 56 minutes ago
  No doubt reflection has been built with other use cases in mind, but it sure would have been nice just to have std::to_string(enum)
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  • bluGill 16 minutes ago
    C++ conference speakers (including keynotes) are now begging everyone to stop using enum to string in their example. While they are a simple and easy to understand example, reflection is for much more interesting problems. I can't think of any other example that I would type into a comment box or put on a slide.
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    • surajrmal 11 minutes ago
      Anybody the derive traits rust has are a good demo.
• sagacity 4 hours ago
  Oof, that first example (the idiomatic C++26 way) looks so foreign if you're mostly used to C++11.
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  • randusername 46 minutes ago
    I was a fool to assume that the same forces shaping the ugliness of C++ syntax would not also be at work in C++ 26.
  • bluGill 15 minutes ago
    You realize c++11 is closer in age to C++98 than C++26?
  • ginko 1 hour ago
    Is it? I'm mostly used to (pre-)C++11 and the only unusual operators I see are ^^T (which I presume accesses the metadata info of T) and [:e:] (which I assume somehow casts the enumerator metadata 'e' to a constant value of T).

    And template for but I assume that's like inline for like in zig.

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    • CamouflagedKiwi 42 minutes ago
      requires is also new (not sure exactly when that appeared, it's after the last time I wrote C++ in anger) although I think it's fairly clear what it means. I can only guess at the other two.

      Not familiar with Zig but AFAICT `inline for` is about instructing the compiler to unroll the loop, whereas `template for` means it can be evaluated at compile time and each loop iteration can have a different type for the iteration variable. It's a bit crazy but necessary for reflection to work usefully in the way the language sets it up.

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      • ginko 34 minutes ago
        Zig's inline for is also evaluated at comptime:

        https://ziglang.org/documentation/master/#inline-for
• king_geedorah 27 minutes ago
  Another win for X macros and for C style in general, though the author didn’t declare it as such.
• jesgran 4 hours ago
  [dead]