🧩 Lesson 7: Templates (Generic Programming)

⏱️ Estimated time: 25 minutes | Difficulty: Advanced

What Are Templates?

Templates let you write generic code that works with any data type. Write once, use with int, double, string, or any type!

Function Templates

#include <iostream>
using namespace std;

template <typename T>
T getMax(T a, T b) {
    return (a > b) ? a : b;
}

int main() {
    cout << getMax(10, 20) << endl;       // 20 (int)
    cout << getMax(3.14, 2.71) << endl;   // 3.14 (double)
    cout << getMax('a', 'z') << endl;     // z (char)
    return 0;
}

Class Templates

template <typename T>
class Box {
    T value;
public:
    Box(T v) : value(v) {}
    T getValue() { return value; }
    void display() { cout << "Box: " << value << endl; }
};

int main() {
    Box<int> intBox(42);
    Box<string> strBox("Hello");
    Box<double> dblBox(3.14);

    intBox.display();  // Box: 42
    strBox.display();  // Box: Hello
    dblBox.display();  // Box: 3.14
    return 0;
}

Multiple Template Parameters

template <typename K, typename V>
class Pair {
    K key;
    V value;
public:
    Pair(K k, V v) : key(k), value(v) {}
    void display() {
        cout << key << ": " << value << endl;
    }
};

Pair<string, int> age("Alice", 25);
Pair<int, double> score(1, 95.5);
age.display();    // Alice: 25
score.display();  // 1: 95.5