Member Avatar for khotso

at school,I was given the class aName and asked to overload the input operator.the class has declared surname as type of char* and the surname is input from the keyboard and it must not be empty.please help me with the code.the class has declared the operator as its friend

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  • Latest Post Latest Post by Ancient Dragon

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The original posts correctly flag two separate problems: memory-management with raw char* members, and incorrect stream-operator signatures. correctly warned that copying the pointer only copies the address (not the characters). also noted allocation/copying and that the stream operators should return references. Those fixes are necessary, but a much simpler and safer approach in modern C++ is to use std::string for the members and then implement the I/O operators to validate non-empty surname.

Example (safer, minimal change to behavior):

#include <iostream>
#include <string>
#include <sstream>

struct aName {
    std::string surname;
    std::string firstname;
};

std::istream& operator>>(std::istream& is, aName& n) {
    std::string line;
    if (!std::getline(is, line)) return is;
    std::istringstream iss(line);
    if (!(iss >> n.surname)) { is.setstate(std::ios::failbit); return is; }
    std::getline(iss, n.firstname);
    if (!n.firstname.empty() && n.firstname.front() == ' ') n.firstname.erase(0,1);
    if (n.surname.empty()) is.setstate(std::ios::failbit);
    return is;
}

std::ostream& operator<<(std::ostream& os, const aName& n) {
    os << n.surname;
    if (!n.firstname.empty()) os << ' ' << n.firstname;
    return os;
}

Notes and troubleshooting:

  • Using std::string avoids manual allocation, leaks, and double-delete bugs. If legacy char* is required, implement destructor, copy constructor and copy-assignment (Rule of Three) so deep copies happen and destructors free owned memory. See Rule of Three.
  • Comparing a char* parameter to an empty string literal tests pointer equality, not content. To test content, check for null pointer and then aSurname[0] == '\0' (or use strcmp).
  • Operator semantics: streaming operators should return the stream by reference. For interactive re-prompting, handle the input loop in calling code rather than embedding repeated prompts inside operator>>; alternatively, make operator>> set the stream’s failbit on invalid input so the caller can decide how to recover.

This preserves the requirement that surname not be empty while avoiding raw-pointer pitfalls pointed out by and implementing the corrected operator semantics mentioned by .

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Member Avatar for Ancient Dragon

post the class then we can discuss how to implement to >> operator.

Member Avatar for khotso

post the class then we can discuss how to implement to >> operator.

class aName
{
friend std::istream operator>>(std::istream & input,aName &name);
/*input the name from the standard input stream like the keyboard and the name is never empty*/
friend std::ostream operator<<(std::ostream & output,aName name);
//it displays the name on the standard output like the screen

private:
char*surname,
       *firstname;

public:aName(char *aSurname,char*aFirstname);
void set(char *aSurname,char* afirstname)
{
if(aSurname=="")
  surname="";
else
surname=aSurname;
if(afirstname=="")
firstname="";
else
firstname=afirstname;
};
Member Avatar for Member #248612

Warning! This line

surname=aSurname;

just copies the pointer not the content!!!

Member Avatar for Ancient Dragon

>>surname=aSurname;

First you have to allocate space for surname then call strcpy() to copy it

surname = new char[strlen(aSurname)+1];
strcpy(surname, aSurname);
Member Avatar for Ancient Dragon

The two friend functions must return a reference to the istream and ostream objects. Here's correction

#include <iostream>
#include <string>
#include <cstring>
using namespace std;
#pragma warning( disable: 4996) // only needed for VC++ 2008 compiler

class aName
{
friend std::istream& operator>>(std::istream & input,aName &name);
/*input the name from the standard input stream like the keyboard and the name is never empty*/
friend std::ostream& operator<<(std::ostream & output,aName name);
//it displays the name on the standard output like the screen

private:
char*surname,
    *firstname;

public:
    aName() { surname = NULL; firstname = NULL;}
    aName(char *aSurname,char*aFirstname)
    {
        surname = NULL; firstname = NULL;
        set(aSurname, aFirstname);
    }

    void set(char** name, const char* aName)
    {
        if( *name != NULL)
            delete[] *name;
        *name = NULL;
        if( aName != NULL)
        {
            *name = new char[strlen(aName)+1];
            strcpy(*name, aName);
        }
    }
    void set(const char *aSurname,const char* afirstname)
    {
        set(&surname, aSurname);
        set(&firstname, afirstname);
    }
};

istream& operator>>(istream& in, aName& nm)
{
    // TODO:  complete this function.
    return in;
}

int main()
{
    aName n;
    cin >> n;
}

[edit]Oops! I just noticed I did half your homework:(

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