Use of the & operator in C++ function signatures

Question

I\'m currently reading through Accelerated C++ and I realized I don\'t really understand how & works in function signatures.

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Answer 1

The & character in C++ is dual purpose. It can mean (at least)

1. Take the address of a value
2. Declare a reference to a type

The use you're referring to in the function signature is an instance of #2. The parameter string& str is a reference to a string instance. This is not just limited to function signatures, it can occur in method bodies as well.

void Example() {
  string s1 = "example";
  string& s2 = s1;  // s2 is now a reference to s1
}

I would recommend checking out the C++ FAQ entry on references as it's a good introduction to them.

• https://isocpp.org/wiki/faq/references