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Item 1: View C++ as a federation of languages

Concept​

C++ is not a single unified language — it's a federation of four sub-languages, each with its own conventions:

  1. C — blocks, statements, preprocessor, built-in types, arrays, pointers
  2. Object-Oriented C++ — classes, encapsulation, inheritance, polymorphism, virtual functions
  3. Template C++ — generic programming, template metaprogramming (TMP)
  4. The STL — containers, iterators, algorithms, function objects

Rules for effective programming vary depending on which sub-language you're using. For example, pass-by-value is efficient for built-in C types, but pass-by-reference-to-const is generally preferred in Object-Oriented C++.

Code Example​

// Sub-language 1: C
void c_sublanguage() {
    int arr[] = {3, 1, 4, 1, 5};
    int* p = arr;
}

// Sub-language 2: Object-Oriented C++
class Shape {
public:
    virtual ~Shape() = default;
    virtual double area() const = 0;
};

// Sub-language 3: Template C++
template <typename Container>
void print_all(const Container& c) { /* ... */ }

// Sub-language 4: The STL
void stl_sublanguage() {
    std::vector<int> v = {5, 2, 8, 1, 9, 3};
    std::sort(v.begin(), v.end());
}

Full source code

Things to Remember​

  • Rules for effective C++ programming vary, depending on the part of C++ you are using.
  • Item 20 — Pass-by-reference-to-const vs pass-by-value (rules differ per sub-language)
  • Item 41 — Implicit interfaces and compile-time polymorphism (Template C++)
  • Item 54 — The standard library (STL sub-language)