What does a=&*A mean in C++ (in which A is a pointer)?

Question

I come across this instruction

a=&*A;

in a piece of C++ code, where A is a pointer. Can anyone explain its semantics and in what way it is different from a=A?

C or C++? Very important difference here! (Unless everything here is built-in types. If that's the case, state it.) — Baum mit Augen, Aug 08 '16 at 12:20
Remember that C++ have operator overloading, so it's impossible to answer without knowing what `A` is and what operators are overloaded for it. — Some programmer dude, Aug 08 '16 at 12:22

score 9 · Accepted Answer · answered Aug 08 '16 at 12:26

If A is an iterator, then *A gives you the value of what the iterator is "pointing" to. Then the & operator is applied to that value to get an address to the value. Unless the & operator was overloaded.

Simple and somewhat stupid example:

struct Foo
{
    // Some data...
};

std::vector<Foo> vector_of_foo;

// Code to populate vector_of_foo

for (auto A = vector_of_foo.begin(); A != vector_of_foo.end(); ++A)
{
    Foo* a = &*A;
    // Do something that requires a pointer to Foo...
}

The example is more than 10000 words :) Thanks. – zell Aug 08 '16 at 12:36 — zell, Aug 08 '16 at 12:36

score 3 · Answer 2 · answered Aug 08 '16 at 12:25

Operator * can be overloaded, and it usually is overloaded for iterators and smart pointers.

If A is a class with pointer-like semantics and you want to get raw pointer to value it points to, then you have to apply operator* (to access value) and then operator& (to retrieve address).

This is most likely usecase when you will see construct like that. It is impossible to know more without knowing what A and related classes is: * can be overloaded to do something else and & can be overloaded too.

score 2 · Answer 3 · answered Aug 08 '16 at 12:25

2

Assuming A is kind of object, then probably * is an operator.

If A is say iterator, then a could be the address of current element where the iterator points.

answered Aug 08 '16 at 12:25

Nick

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score -1 · Answer 4 · answered Aug 08 '16 at 12:54

-1

Here is the explanation which i learnt in my college. & = "address of"

= "value at"

&*A = from left to right "Address of , Value at A".

answered Aug 08 '16 at 12:54

user3111607

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What does a=&*A mean in C++ (in which A is a pointer)?

4 Answers4