Does a colon before the body of a constructor indicate inheritance

Question

I wish to understand how the code below runs. Is aproxy inheriting from mPtr? Is struct array returning a method, aproxy, in struct aproxy?

struct aproxy {
    aproxy( int & r ) : mPtr( & r ) {}  // is this inheritance? 
    void operator = ( int n ) {
        if ( n > 1 ) {
            throw "not binary digit";
        }
        *mPtr = n;
    }
    int * mPtr;
};

struct array {      
    int mArray[10];
    aproxy operator[]( int i) {      
        return aproxy( mArray[i] );   // what does this line do?
    }
};

int main() {
    try {
        array a;
        a[0] = 1;   
        a[0] = 42;      
    }
    catch( const char * e ) {
        cout << e << endl;
    }
}

Answer 1

is this inheritance?

aproxy( int & r ) : mPtr( & r ) {} 

This is not inheritance, it is the initialization of data member mPtr in a constructor initialization list. You are initializing a pointer to int to point to the address of an int.

return aproxy( mArray[i] );   // what does this line do?

It creates an aproxy instance, initialized with the value of mArray[i], and returns it by value.

Answer 2

No, there is no inheritance here. And you cannot "return a method"; "method" is a colloquial name for a "member function".