Function Templates, Class Templates & Custom Namespaces

Explanation

Templates are executed at compile-time via template instantiation. The compiler generates specialized machine code for each unique type parameter combination, avoiding runtime boxing/unboxing overhead while preserving compile-time type safety.

Key points

• Function Templates: template T findMax(T a, T b) generates concrete functions on-demand.
• Class Templates: template class Stack creates type-safe collections for int, float, or custom objects.
• Namespaces: Prevent global identifier naming collisions in large projects (namespace MyProject { int value; }).
• Using Directives: using namespace std brings entire namespace into scope; using std::cout brings specific symbols.

Example

Code examples

// Generic Stack Implementation Using C++ Class Template
#include <iostream>
using namespace std;

template <typename T, int MAX_SIZE = 100>
class GenericStack {
private:
    T elements[MAX_SIZE];
    int topIndex;

public:
    GenericStack() : topIndex(-1) {}

    bool push(T val) {
        if (topIndex >= MAX_SIZE - 1) return false;
        elements[++topIndex] = val;
        return true;
    }

    T pop() {
        if (topIndex < 0) throw runtime_error("Stack Underflow");
        return elements[topIndex--];
    }
};

int main() {
    GenericStack<int> intStack;
    intStack.push(10); intStack.push(20);
    cout << intStack.pop() << endl;

    GenericStack<string> strStack;
    strStack.push("Purbanchal"); strStack.push("University");
    cout << strStack.pop() << endl;
    return 0;
}

Exam questions

• [8 Marks] Design a generic Stack class using C++ class templates with push, pop, and isEmpty operations.
• [7 Marks] What are namespaces in C++? How do they prevent identifier collisions? Explain with code snippets.