Function Review

Objectives

1. Review function terms.
2. Review function syntax
3. Review function parameters

Notes

• Most of this is from my knowledge
  • cppreference has an extensive article.
  • cplusplus.com has a more introductory article.

• #include < iostream>
  using namespace std;
  someType Function1(int param1, float & param2);
  int main() {
     int x;
     int a;
     float b;
  
     x = Function1(a,b);
     return 0;
  }
  void Function1(int param1, float & param2){
      int x;
      someType returnValue;
  
      return returnValue;
  } 

• Line 3
  • This is called the function prototype
  • It is where the function is declared, or function declaration.
  • for now type identifier(parameter list)
  • The type can be void or any other data type.
• Parameter lists
  • [const] type [&] [identifier] [, ...]
  • The simplest type identifier
    • EX: int x
    • The parameter x is of type int
    • It is a pass by value.
    • This means that a copy of the argument in this position is made for the function.
    • And the value in the calling function is unchanged.
  • Pass by reference
    • EX: int & x
    • The parameter x is of type int
    • x refers back to the corresponding argument.
    • Changes to x are reflected in the corresponding argument.
  • Pass by constant reference
    • EX: const int & x
    • The parameter x refers to the corresponding argument, but no changes to x are permitted (by the compiler)
    • This is used to avoid copying large data.
  • Pass by pointer
    • EX: int x[]
    • This is the exception to the rule.
    • Since x is an array, it is pass by pointer.
    • Changes to x are changes to the corresponding argument.
  • Note, parameters do not have to be named in function prototypes.
• Line 5 is the function invocation.
  • a and b are arguments
  • Arguments must correspond to parameters
    • I number: there must be the same number of parameters as arguments.
    • By position:
      • The types must match or be coercable.
        • The first parameter is an int
        • you can pass an int, short or char in with no problem.
        • You can pass a long, float, ... with type casting
        • You can not pass a string, stream, ...
      • The variability must match.
        • The second parameter is pass by reference.
        • You can pass any variable (where the type is acceptable as above)
        • You can not pass a literal constant or a named constant.
• Lines 7-12 are the function implementation or definition.
  • param1 and param2 are parameters,
    • They are defined within the scope of the function.
    • And could be considered variables in the function.
  • Line 8 and 9 define local variables x and returnValue
    • The scope or where these variables can be used is the body of the function.
    • The lifetime or when these variables have value is when the body of the function is executing.
    • When the function exits, these variables are destroyed.