C++ Functions

  • Code can be organized into functions
  • Functions create a scope {}
  • Single return value from a function
  • Any number of input variables of any type
  • Should do only one thing and do it right
  • Name must show what the function does
  • Is small enought to see all the code at once
  • Name clearly states what the function does

Function declaration sets up an interface.

void FuncName(int param);
  • Move all declarations to header files (*.h)

Function definition holds the implementation of the function that can even be hidden from the user.

void FuncName(int param) {
  // Implementation details.
  cout << "This function is called FuncName! ";
  cout << "Did you expect anything useful from it?";
  • Implementation goes to *.cpp or *.cc

Functions can accept default arguments. Only set in declaration not in definition.

Passing big objects

By default in C++, objects are copied when passed into functions. If objects are big it might be slow. Pass by reference to avoid copy.

void DoSmth(std::string huge_string ); // Slow. Copy
void DoSmth(std::string& huge_string ); // Faster. Pass by reference

Pass const reference to the function. Passed object stays intact.

void DoSmth(const std::string& huge_string );

Avoid using non-const reference.

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