4 ms·

I've only been using C++ for a few months, but it's my opinion that all function parameters should have been "const &" by default (except for maybe primitive ty

by fferen 15y ago

I've only been using C++ for a few months, but it's my opinion that all function parameters should have been "const &" by default (except for maybe primitive types). Const correctness has helped me spot some nasty bugs, and it's too easy to accidentally forget the "&" and pass horrendously large structures by value, which must go through a copy constructor and destructor with every call. Plus, it gets really tedious typing "const Mat &src" a million times (guess which library I'm using, lol).

octopus 15y ago
In C++11 "type const &name" can be simply replaced with "type name", no performance penalty involved.
- ajax77 15y ago
  That's simply not the case.. In general, the "no penalty" holds true for primitive data types, and when passing an r-value instance of a class that has a move copy constructor defined. In the case where your object is an expensively constructed l-value, it is preferable to pass by const reference rather than value (assuming you plan to use the object later... otherwise you could indeed pass using std::move semantics).
  - octopus 15y ago
    In C++11 you are supposed to use move semantics in your own classes. I'm not 100% sure but I think the standard require that the STL use move semantics.
    - cageface 15y ago
      Yes but this is one more thing you have to think about when implementing a class in C++ and one more chance to screw it up. It makes vanilla C and raw pointers look a lot more appealing, to be honest.
      - octopus 15y ago
        Actually I think C++11 is a simpler language than C++03 or C++98. The problem is that we need to un-learn what we know and learn the new way of doing things.
        cageface 15y ago
        C++11 is simpler for the casual user of classes but I'm not so sure it's easier if you're implementing a lot of classes yourself. I disable assignment and copying in all my classes by default unless I have a really good reason to implement them and I still pass by const & for types I define myself.

by fferen 15y ago

octopus 15y ago

In C++11 "type const &name" can be simply replaced with "type name", no performance penalty involved.

ajax77 15y ago
That's simply not the case.. In general, the "no penalty" holds true for primitive data types, and when passing an r-value instance of a class that has a move copy constructor defined. In the case where your object is an expensively constructed l-value, it is preferable to pass by const reference rather than value (assuming you plan to use the object later... otherwise you could indeed pass using std::move semantics).
- octopus 15y ago
  In C++11 you are supposed to use move semantics in your own classes. I'm not 100% sure but I think the standard require that the STL use move semantics.
  - cageface 15y ago
    Yes but this is one more thing you have to think about when implementing a class in C++ and one more chance to screw it up. It makes vanilla C and raw pointers look a lot more appealing, to be honest.
    - octopus 15y ago
      Actually I think C++11 is a simpler language than C++03 or C++98. The problem is that we need to un-learn what we know and learn the new way of doing things.
      - cageface 15y ago
        C++11 is simpler for the casual user of classes but I'm not so sure it's easier if you're implementing a lot of classes yourself. I disable assignment and copying in all my classes by default unless I have a really good reason to implement them and I still pass by const & for types I define myself.