Project 11.19 Section 11 ⚡ Embedded Relevance: Core Templates std::swap Pass-by-Reference

11.19 Pass-by-Reference & Zero-Copy Value Exchanges

Executive Summary: Implementing generic swap templates using reference passing without heap allocations.

💻 1. Annotated Source Code

#ifndef SWAPPER_H
#define SWAPPER_H

template <class T>
class Swapper {
	public:
		Swapper(T first, T second);
		void swap();
		T getFirst() const;
		T getSecond() const; 

	private:
		T first;
		T second;
};


template <class T>
Swapper<T>::Swapper(T first, T second) : first(first), second(second) {}

template <class T>
void Swapper<T>::swap() {
	T temp = first;
	first = second;
	second = temp;
}

template <class T>
T Swapper<T>::getFirst() const {
	return first;
}

template <class T>
T Swapper<T>::getSecond() const {
	return second;
}

#endif

#include <iostream>
#include <string>
#include "Swapper.h"
using namespace std;

int main() {
	Swapper<int> intSwapper(5, 10);
	Swapper<string> stringSwapper("John", "Bob");

	cout << "Before swap:" << endl;
	cout << "\t" << intSwapper.getFirst() << ", "
		<< intSwapper.getSecond() << endl;
	cout << "\t" << stringSwapper.getFirst() << ", "
		<< stringSwapper.getSecond() << endl;


	intSwapper.swap();
	stringSwapper.swap();

	cout << "\nAfter swap:" << endl;
	cout << "\t" << intSwapper.getFirst() << ", "
		<< intSwapper.getSecond() << endl;
	cout << "\t" << stringSwapper.getFirst() << ", "
		<< stringSwapper.getSecond() << endl;


	return 0;
}

📐 2. Architecture & UML Class Model

📐 Templated Swapper<T> Generic Pair Manipulation Model

+ Public - Private # Protected

<<template class>> Swapper<T> Generic Swapper

Attributes / Data Members

-first : T

-second : T

Operations / Methods

+Swapper(a: const T&, b: const T&)

+swap() : void[std::swap(first, second)]

+getFirst() : T const

+getSecond() : T const

📚 3. Core C++ Concepts Deep-Dive

Generic Reference Swapping

Using template references T& allows modifying caller variables directly without copies.

⚡ 4. Embedded Systems & Hardware Reality

Register Swaps

Compilers optimize reference swaps directly into CPU register instructions (e.g. MOV/REV).

💡 5. Production-Ready Embedded Refactoring

💡 Production-Ready Refactor

template <typename T>
void fastSwap(T& a, T& b) noexcept {
    T tmp = std::move(a); a = std::move(b); b = std::move(tmp);
}

📝 Knowledge Verification Quiz

Test your understanding of the C++ concepts and embedded microcontroller trade-offs covered in this guide. Click any option for instant feedback.

Q1. Why is pass-by-reference essential in template swap functions?

A To avoid expensive copies and modify the original variables in-place.

B To allocate pointers dynamically.

C To enable runtime polymorphism.

D To store values in ROM.

Detailed Explanation: Pass-by-reference enables in-place modification and avoids copying large payloads.