const is pointless when the argument is passed by value since you will not be modifying the caller’s object. Wrong. It’s about self-documenting your code and your assumptions. If your code has many people working on it and your functions are non-trivial then you should mark const any and everything that you can. When writing … Read more
Arrays on the type level An array type is denoted as T[n] where T is the element type and n is a positive size, the number of elements in the array. The array type is a product type of the element type and the size. If one or both of those ingredients differ, you get … Read more
Huge difference. As the name implies, a double has 2x the precision of float[1]. In general a double has 15 decimal digits of precision, while float has 7. Here’s how the number of digits are calculated: double has 52 mantissa bits + 1 hidden bit: log(253)÷log(10) = 15.95 digits float has 23 mantissa bits + … Read more
The objects in the std::set are stored as const StudentT. So when you try to call getId() with the const object the compiler detects a problem, mainly you’re calling a non-const member function on const object which is not allowed because non-const member functions make NO PROMISE not to modify the object; so the compiler … Read more
You have to define your static member outside the class definition and provide the initializer there. First // In a header file (if it is in a header file in your case) class A { private: static const string RECTANGLE; }; and then // In one of the implementation files const string A::RECTANGLE = “rectangle”; … Read more
Using C++11: #include <map> using namespace std; map<int, char> m = {{1, ‘a’}, {3, ‘b’}, {5, ‘c’}, {7, ‘d’}}; Using Boost.Assign: #include <map> #include “boost/assign.hpp” using namespace std; using namespace boost::assign; map<int, char> m = map_list_of (1, ‘a’) (3, ‘b’) (5, ‘c’) (7, ‘d’);
This comes in useful when you have global variables. You declare the existence of global variables in a header, so that each source file that includes the header knows about it, but you only need to “define” it once in one of your source files. To clarify, using extern int x; tells the compiler that … Read more
Well … Sort of. The easiest is to just use the fact that adjacent string literals are concatenated by the compiler: const char *text = “This text is pretty long, but will be ” “concatenated into just a single string. ” “The disadvantage is that you have to quote ” “each part, and newlines must … Read more
In C++, there are three distinct character types: char signed char unsigned char If you are using character types for text, use the unqualified char: it is the type of character literals like ‘a’ or ‘0’ (in C++ only, in C their type is int) it is the type that makes up C strings like … Read more
Foo foo2(); change to Foo foo2; You get the error because compiler thinks of Foo foo2() as of function declaration with name ‘foo2’ and the return type ‘Foo’. But in that case If we change to Foo foo2 , the compiler might show the error ” call of overloaded ‘Foo()’ is ambiguous”.