11 ms·

for (auto [s, n]: my_map) copies all the data needlessly, better to use for (const auto& [s, n]: my_map)

• heywhatupboys 3y ago
  what a language
  • lionkor 3y ago
    just consider const reference to be the default for non-primitive types
    • a_e_k 3y ago
      My rule of thumb is to use const references when the sizeof the type is larger than the sizeof a pointer or reference.
      • repsilat 3y ago
        Might be worth using values/copies even a bit bigger, so long as it's "simple" data. This[1] short post argues for passing `std::string_view` (~2 pointers) by value, for - Omitting pointer indirections (loads), - Not forcing the pointee to have an address (i.e. gotta be in memory, not just registers), and - Eliminating aliasing questions, potentially leading to better codegen if the function isn't inlined. 1: https://quuxplusone.github.io/blog/2021/11/09/pass-string-view-by-value/ https://quuxplusone.github.io/blog/2021/11/09/pass-string-vi...
• nuancebydefault 3y ago
  That's why some newer languages have 'const are the default'.
  • Tommstein 3y ago
    I'm pretty sure it's the reference that makes the data not be copied.
    • nuancebydefault 3y ago
      Copying the data to a const makes little sense in this case. The extra & choice that has emerged makes things more complicated than needed. The sad faith of this old language.
    • nly 3y ago
      Without the const the key would still be const.