Re: Better way to use istream to read an ascii value into a char.

From:
"Markus Schoder" <a3vr6dsg-usenet@yahoo.de>
Newsgroups:
comp.lang.c++
Date:
4 May 2006 12:11:20 -0700
Message-ID:
<1146769880.776128.109260@y43g2000cwc.googlegroups.com>
Jim Langston wrote:

In one of my files I am outputting the value of a char into a human readable
file. That is,
char a = 123;
std::ofstream CharFile( ("Players\\" + Name + ".char").c_str());
if ( CharFile.is_open() )
   CharFile << (int) a;

So the file has the character a stored as "123".

That was the easy part, now comes the fun of reading it back into the char.

I tried a number of things and finally wound up doing this:

std::istream& operator >>( std::istream& is, char& Byte )
{
    int temp;
    is >> temp;
    Byte = temp;
    return is;
}

char a;
std::ifstream CharFile( ( "Players\\" + CharName + ".char" ).c_str());
if ( CharFile.is_open() )
   CharFile >> a;


[snip]

The thing I don't like about overriding the operator >> for a char, though,
is if I ever want to actually write a char as a byte itself (which I don't
think I will).

I'm just wondering if there is a better way.

I attempted something along the lines of:

std::istream& ReadByteVal( std::istream& is, char& Byte ) {/**/}

and then attempted to use it like

is >> ReadByteVal( is, CChar.Agility ) >> ReadByteVal( is, CChar.Reason ) >>
/**/

but that wouldn't compile, the compiler complaining something about not
finding a call taking an rvalue.

Someone else came up with a horrible looking template that seems to be prone
to errors itself. Anyone have any ideas?


Wrap a char reference in a user defined type and define operator>> for
this type:

#include <iostream>

struct achar
{
  achar(char &c) : c_(c) {}
  char &c_;
};

std::istream &
operator>>(std::istream &is, achar a)
{
  int tmp;
  is >> tmp;
  a.c_ = tmp;
  return is;
}

int
main()
{
  char c;
  std::cin >> achar(c);
  std::cout << c << std::endl;
}

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