C++ FAQ / Section 4 / FAQ 4.9

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Revised Jul 4, 2012

[4.9] What updates were made for the 04/10 release?

2 New FAQs:

• [4.9] What updates were made for the 04/10 release?
  (created)
• [7.7] Can a method directly access the non-public members of another instance of its class?
  (created thanks to a suggestion from Darren Sargent and Vikas Rangarajan)

63 Changed FAQs:

• [2.11] Where can I find the C++ FAQ translated into Polish?
  (updated the Polish translation's URL)
• [4.26] What updates were made for the 06/04 release?
  (updated the Polish translation's URL)
• [4.35] What updates were made for the 09/02 release?
  (updated the Polish translation's URL)
• [8.5] How can you reseat a reference to make it refer to a different object?
  (changed const X* to X const*)
• [10.20] What is the "Named Parameter Idiom"?
  (changed const X& to X const&)
• [10.21] Why am I getting an error after declaring a Foo object via Foo x(Bar())?
  (changed const X& to X const&)
• [12.2] Why should I worry about "self assignment"?
  (changed const X& to X const&)
• [12.3] OK, OK, already; I'll handle self-assignment. How do I do it?
  (clarified the "don't go out of your way to make self-assignment fast" paragraphs at the end thanks to a question from Stan; and changed const X& to X const&)
• [12.4] I'm creating a derived class; should my assignment operator call my base class's assignment operator?
  (changed const X& to X const&)
• [13.1] What's the deal with operator overloading?
  (changed const X& to X const&)
• [13.10] How do I create a subscript operator for a Matrix class?
  (changed const X& to X const&)
• [13.12] I still don't get it. Why shouldn't my Matrix class's interface look like an array-of-array?
  (changed const X& to X const&)
• [15.8] How can I provide printing for my class Fred?
  (changed const X& to X const&)
• [15.9] But shouldn't I always use a printOn() method rather than a friend function?
  (changed const X& to X const&)
• [15.10] How can I provide input for my class Fred?
  (changed const X& to X const&)
• [15.11] How can I provide printing for an entire hierarchy of classes?
  (changed const X& to X const&)
• [15.12] How can I open a stream in binary mode?
  (changed const X& to X const&)
• [16.17] But the previous FAQ's code is SOOOO tricky and error prone! Isn't there a simpler way?
  (changed const X& to X const&)
• [16.18] But the above Matrix class is specific to Fred! Isn't there a way to make it generic?
  (changed const X& to X const&)
• [16.19] What's another way to build a Matrix template?
  (changed const X& to X const&)
• [16.21] How can I force objects of my class to always be created via new rather than as locals or global/static objects?
  (changed const X& to X const&)
• [16.22] How do I do simple reference counting?
  (changed const X& to X const&)
• [16.23] How do I provide reference counting with copy-on-write semantics?
  (changed const X& to X const&)
• [16.24] How do I provide reference counting with copy-on-write semantics for a hierarchy of classes?
  (changed const X& to X const&)
• [17.11] How do I change the string-length of an array of char to prevent memory leaks even if/when someone throws an exception?
  (changed const X& to X const& and const X* to X const*)
• [17.15] What does throw; (without an exception object after the throw keyword) mean? Where would I use it?
  (changed const X& to X const&)
• [18.1] What is "const correctness"?
  (changed const X& to X const& and const X* to X const*)
• [18.4] What does "Fred const* p" mean?
  (changed const X* to X const*)
• [18.5] What's the difference between "Fred const* p", "Fred* const p" and "Fred const* const p"?
  (changed const X* to X const*)
• [18.6] What does "Fred const& x" mean?
  (changed const X& to X const&)
• [18.7] Does "Fred& const x" make any sense?
  (changed const X& to X const&)
• [18.8] What does "const X& x" mean?
  (reversed the sense so X const& is now common and const X& is classic)
• [18.9] What does "const X* x" mean?
  (reversed the sense so X const* is now common and const X* is classic)
• [18.10] What is a "const member function"?
  (changed const X& to X const&)
• [18.11] What's the relationship between a return-by-reference and a const member function?
  (changed const X& to X const&)
• [18.12] What's the deal with "const-overloading"?
  (changed const X& to X const&)
• [18.13] What do I do if I want a const member function to make an "invisible" change to a data member?
  (changed const X* to X const*)
• [18.15] Why does the compiler allow me to change an int after I've pointed at it with a int const*?
  (changed const X* to X const*)
• [18.16] Does "Fred const* p" mean that *p can't change?
  (changed const X* to X const*)
• [18.17] Why am I getting an error converting a Foo** → Foo const**?
  (changed const X* to X const*)
• [21.12] If SortedList has exactly the same public interface as List, is SortedList a kind-of List?
  (changed const X& to X const&)
• [22.5] How do you define a copy constructor or assignment operator for a class that contains a pointer to a (abstract) base class?
  (changed const X& to X const&)
• [23.5] When my base class's constructor calls a virtual function on its this object, why doesn't my derived class's override of that virtual function get invoked?
  (changed const X& to X const&)
• [23.6] Okay, but is there a way to simulate that behavior as if dynamic binding worked on the this object within my base class's constructor?
  (changed const X& to X const&)
• [26.13] What should be returned from a function?
  (changed const X* to X const*)
• [27.10] Are there any lint-like guidelines for C++?
  (changed const X& to X const&)
• [27.14] Should I use "unusual" syntax?
  (changed const X& to X const&)
• [28.4] Should I buy one book, or several?
  (fixed a misspelling thanks to Nigel Colpitts)
• [29.17] Why doesn't my floating-point comparison work?
  (added #include <cmath> to make sure the compiler uses the std::abs(double) overload, rather than std::abs(int))
• [32.5] How can I call a non-system C function f(int,char,float) from my C++ code?
  (changed const X* to X const*)
• [33.13] What the heck is a functionoid, and why would I use one?
  (changed const X& to X const&)
• [33.14] Can you make functionoids faster than normal function calls?
  (changed const X& to X const&)
• [35.2] What's the syntax / semantics for a "class template"?
  (changed const X& to X const&)
• [35.7] My template function does something special when the template type T is int or std::string; how do I write my template so it uses the special code when T is one of those specific types?
  (changed const X& to X const&)
• [35.8] Huh? Can you provide an example of template specialization that doesn't use foo and bar?
  (changed const X& to X const&)
• [35.9] But most of the code in my template function is the same; is there some way to get the benefits of template specialization without duplicating all that source code?
  (changed const X& to X const&)
• [35.16] Why do I get linker errors when I use template friends?
  (changed const X& to X const&)
• [37.3] How can I find a Fred object in an STL container of Fred* such as std::vector<Fred*>?
  (changed const X& to X const& and const X* to X const*)
• [39.1] How do I convert a value (a number, for example) to a std::string?
  (changed const X& to X const&)
• [39.2] How do I convert a std::string to a number?
  (changed const X& to X const&)
• [39.3] Can I templatize the above functions so they work with other types?
  (changed const X& to X const&)
• [39.5] What should be done with macros that have multiple lines?
  (rewrote to reflect current C++ compilers)
• [39.11] How can I create two classes that both know about each other?
  (fixed the return type in the prose from Fred to Fred* thanks to Mark Ruvald)