[boost] Fwd: lexical_cast problem with custom string class

7 Aug 2006

      Sorry, never got a reply in the users list,

So fwd'ed here...

-------- Original Message --------
Subject: lexical_cast problem
Date: Fri, 4 Aug 2006 16:53:10 +1200
From: shams <shams@orcon.net.nz>
To: boost-users@lists.boost.org

Hi,

Here is a sample custom string class that I am tring to get working with
lexical_cast but it gives me compile errors. Can you please see what I am doing
wrong here. More explanation below.

OTOH if I use a custom lexical_cast using wstringstream it works fine.

// main.cpp
#include <string>
#include <iostream>

#include "boost_1_33_1/boost/lexical_cast.hpp"

using namespace std;

class String : public wstring
{
public:
	String()
	{
	}

	String(const wchar_t *str) : wstring(str)
	{
	}

	String& operator=(const String& Rhs)
	{
		return static_cast<String&>(wstring::operator=(Rhs));
	}
};

// This is commented cause lexical_cast wants bool return value.
#if 0
template<class OutputStream>
OutputStream& operator<<(OutputStream &o, const String &s)
{
	return o << s.c_str();
}
#endif

template<class OutputStream>
bool operator<<(OutputStream &o, const String &s)
{
	o << s.c_str();

	return true;
}

// This is commented cause lexical_cast wants bool return value.
#if 0
template<class InputStream>
InputStream& operator>>(InputStream &i, String &s)
{
	wstring ws;

	i >> ws;

	s.assign(ws);

	return i;
}
#endif

template<class InputStream>
bool operator>>(InputStream &i, String &s)
{
	wstring ws;

	i >> ws;

	s.assign(ws);

	return true;
}

int main()
{
	// This line causes errors both on MSVC and GCC.
	wcout << boost::lexical_cast<String>(10);

	// These lines DONT cause errors and work ok.
	String s = L"hello";

	wcout << s;
	wcout << endl;

	wcin >> s;
	wcout << s;
	wcout << endl;

	return 0;
}