When is a const reference better than pass-by-value in C++11?

by

The general rule of thumb for passing by value is when you would end up making a copy anyway. That is to say that rather than doing this:

void f(const std::vector<int>& x) {
    std::vector<int> y(x);
    // stuff
}

where you first pass a const-ref and then copy it, you should do this instead:

void f(std::vector<int> x) {
    // work with x instead
}

This has been partially true in C++03, and has become more useful with move semantics, as the copy may be replaced by a move in the pass-by-val case when the function is called with an rvalue.

Otherwise, when all you want to do is read the data, passing by const reference is still the preferred, efficient way.

More Related Contents:

  1. How do I take values from text file and input into a 2D array? c++
  2. const vs constexpr on variables
  3. How is “=default” different from “{}” for default constructor and destructor?
  4. What is a subnormal floating point number?
  5. Pointers in c++ after delete
  6. Why does std::move prevent RVO (return value optimization)?
  7. Narrowing conversions in C++0x. Is it just me, or does this sound like a breaking change?
  8. Can the use of C++11’s ‘auto’ improve performance?
  9. Why are by-value parameters excluded from NRVO?
  10. What is the difference between packaged_task and async
  11. Populate An Array Using Constexpr at Compile-time
  12. Why should I use std::async?
  13. How to use C++11 enum class for flags
  14. Are int8_t and uint8_t intended to be char types?
  15. Double delete in initializer_list vs 2013
  16. Need iterator when using ranged-based for loops
  17. How can std::unique_ptr have no size overhead?
  18. How to enforce the ‘override’ keyword?
  19. C++11 operator”” with double parameter
  20. std::remove_const with const references
  21. Comparing 3 modern c++ ways to convert integral values to strings
  22. Using char16_t and char32_t in I/O
  23. Uniform initialization fails to copy when object has no data members
  24. constexpr initialization of array to sort contents
  25. What is the purpose of std::function and how to use it?
  26. Which greedy initializer-list examples are lurking in the Standard Library?
  27. How does std::forward receive the correct argument?
  28. Undefined reference to process(std::__cxx11::basic_string … ) when compiling affdex linux sample applications
  29. C++ view types: pass by const& or by value?
  30. Overload resolution with ref-qualifiers

Leave a Comment