problem_10.md

Staying in bounds << | Home | >> Better Initialization

Problem 10: I want a vector of chars

2017-10-03

Start over? No

Introduce a major abstraction mechanism, templates

• Generalize overtypes

Vector.h

namespace CS246E {
    template<typename T> class Vector {
            size_t n, cap;
            T* theVector;

        public:
            Vector();
            ...
            void push_back(T n);
            T &operator[](size_t i);
            const T &operator[] const(size_t)

            using iterator = T*;
            using const_iterator = const T*;
            // etc.
    };

    template<typename T> Vector<T>::vector() n{0}, cap{1}, theVector{new T[cap]} {}
    template<typename T> void push_back(T n) {...}
    /// etc.
}

Note: For templates, the implementation goes in .h file

main.cc

int main() {
    Vector<int> v;  // Vector of ints
    v.push_back(1);
    ...
    Vector<char> w; // Vector of chars
    v.push_back('a');
    ...
}

• Semantics:
  • The first time the compile encounters Vector<int>, it creates a version of the vector code where int replaces T and compiles that new class
  • Can't do that unless it has all the details about the class
  • So implementation must be available in .h
  • Can also write bodies inline

---

Staying in bounds << | Home | >> Better Initialization