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STL string, iostream, and cout of class info

Posted on 2002-03-26
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Last Modified: 2013-11-20
I'm an STL newbie, and I'm tring to write a simple program to cout a class that has an std::string in it

Here's a program that works but that doesn't use stl:

// *** compile with cl -GX test00.cpp
#include <iostream.h>
#include <string.h>

class CInfo
{
public:
  CInfo(int key, char* ref);

  friend ostream& operator<<(ostream& s, const CInfo &info);

private:
  int   m_key;
  char  m_ref[20];
};

CInfo::CInfo(int key, char* ref) : m_key(key) { strcpy(m_ref, ref); }

ostream& operator<<(ostream& s, const CInfo &info)
{
  return s << '(' << info.m_ref << ')';
}

int main(void)
{
  cout << "Reached main" << endl;
  CInfo myInfo(123456, "myRef");
  cout << myInfo << endl;
  return 0;
}


Here's the (roughly equivalent) program with std::string.  There's some strangeness with std::ostream, and I get the compiler error for the cout << myInfo << endl;

error C2678: binary '<<' : no operator defined which takes a left-hand operand of type 'class ostream_withassign' (or there is no acceptable conversion)

// *** compile with cl -GX test01.cpp
#include <iostream.h>
#include <string.h>

class CInfo
{
public:
  CInfo(int key, char* ref);

  friend ostream& operator<<(ostream& s, const CInfo &info);

private:
  int   m_key;
  char  m_ref[20];
};

CInfo::CInfo(int key, char* ref) : m_key(key) { strcpy(m_ref, ref); }

ostream& operator<<(ostream& s, const CInfo &info)
{
  return s << '(' << info.m_ref << ')';
}

int main(void)
{
  cout << "Reached main" << endl;
  CInfo myInfo(123456, "myRef");
  cout << myInfo << endl;   // <-- causes compiler error
  return 0;
}

What am I doing incorrectly?  And is the std::outstream necessary?  

TIA
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Question by:ee-user
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2 Comments
 
LVL 86

Accepted Solution

by:
jkr earned 400 total points
ID: 6897278
Make your code read

// *** compile with cl -GX test01.cpp
#include <iostream>
#include <string>

using namespace std;

// etc...

You were using deprecated STL headers (the correct ones don't have the .h extension), and you haven't selected the 'std' namespace...
0
 

Author Comment

by:ee-user
ID: 6897727
duhhhh ...
thx
0

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