Functions recap

Congratulations on completing this section! You've mastered essential function mechanics that every C++ programmer needs to know. Let's review the key concepts.

Function Parameters

Function parameters can be passed by value, reference, or address. Use pass by value for fundamental types and enumerators. Use pass by reference for structs, classes, or when the function needs to modify an argument. Use pass by address for pointers or built-in arrays. Always make pass by reference and pass by address parameters const when possible.

Return Values

Return values can be returned by value, reference, or address. Return by value is the default choice. Return by reference or address can be useful with dynamically allocated data, structs, or classes. When returning by reference or address, verify that the returned object won't go out of scope.

Function Pointers

Function pointers allow passing functions as arguments to other functions. This enables callers to customize behavior, such as specifying how a list should be sorted.

Dynamic Memory

Dynamic memory is allocated on the heap and must be manually managed using new and delete.

The Call Stack

The call stack tracks all active functions from program start to the current execution point. Local variables are stack-allocated. The stack has a limited size. std::vector can implement stack-like behavior.

Recursive Functions

Recursive functions call themselves and must include a termination condition (base case) to prevent infinite recursion.

Command Line Arguments

Command line arguments let users or programs pass data to your program at startup. They're always C-style strings and must be converted to numeric types if needed.

Ellipsis

Ellipsis allow variable argument counts but disable type checking and don't track argument count. Avoid them in modern C++ - use parameter packs or variadic templates instead.

Lambda Functions

Lambda functions are anonymous functions that can be nested inside other functions. They work exceptionally well with the algorithms library and don't need names.

Key Terminology

  • Pass by value: Passing a copy of the argument to the function
  • Pass by reference: Passing a reference to the argument
  • Pass by address: Passing a pointer to the argument
  • Return by value: Returning a copy of the value
  • Return by reference: Returning a reference to avoid copying
  • Return by address: Returning a pointer to an object
  • Function pointer: Pointer that holds the address of a function
  • Dynamic memory: Memory allocated on the heap at runtime
  • Heap: Memory region for dynamic allocation
  • new: Operator for dynamic memory allocation
  • delete: Operator for freeing dynamically allocated memory
  • Call stack: Data structure tracking active function calls
  • Stack allocation: Automatic memory allocation for local variables
  • Recursive function: Function that calls itself
  • Base case: Termination condition for recursive functions
  • Command line arguments: Data passed to a program at startup
  • Ellipsis: Syntax allowing variable argument counts
  • Parameter pack: Modern alternative to ellipsis for variable arguments
  • Variadic template: Template accepting variable number of arguments
  • Lambda function: Anonymous function that can be defined inline

Looking Forward

You've mastered essential function mechanics in C++. These concepts—parameter passing, return values, function pointers, dynamic memory, and lambdas—are fundamental tools for writing efficient, flexible code. As you continue learning, you'll see how these concepts combine with classes and templates to create powerful abstractions.