References

References

A reference is an alias — another name for an existing variable. References are one of C++'s key improvements over C.

Declaring a Reference

int x = 10;
int& ref = x;  // ref is an alias for x

ref = 20;       // changes x through the alias
cout << x;      // 20

A reference must be initialized when declared and cannot be rebound to another variable.

References as Function Parameters

This is the most common use. In C, passing by value creates a copy:

void increment(int x) {
    x++;  // only changes the local copy
}

With a reference, the function modifies the original:

void increment(int& x) {
    x++;  // modifies the original
}

int n = 5;
increment(n);
cout << n;  // 6

const References

Use const T& to pass large objects without copying and without allowing modification. This is the idiomatic C++ way to pass strings and other large objects to functions:

void greet(const string& name) {
    cout << "Hello, " << name << "!" << endl;
    // name = "Bob";  // error — const
}

Without const&, passing a string would copy the entire string. With const&, only a pointer-sized alias is passed.

Return by Reference

Functions can also return references to allow chaining or direct modification:

string& getLonger(string& a, string& b) {
    return a.length() >= b.length() ? a : b;
}

References vs Pointers

Your Task

Write:

1. printPair(const string& first, const string& second) — prints <first> and <second>
2. combine(const string& a, const string& b, const string& sep) — returns a + sep + b

Use them in main to produce the expected output.