Creating my own manipulators (formatting flags for streams)

**bluedog** · 03-14-2006

Hello,

I know that to format output I can use a number of predefined manipulators such as std::boolalpha, std::hex, etc. and use them such as:

Code:

int myNumber = 0;
cout << boolalpha << myNumber << endl;

and that would print false.

I would like to write my own manipulators to format a couple of things that cannot be done with the usual ones, however I've been unable to locate info about how to do this.

In particular I would like to be able to store in a text file certain words and map them to bool values in the program, for example

Code:

bool dropTheBomb = true;
cout << my_manipulator << dropTheBomb << endl;

should print "Yeah!!", and the other way around: I would like to read "Yeah!!" from a string and store it as a bool

Does anybody know how to do this?

**Bench82** · 03-14-2006

manipulators are made from classes which are friends with an overloaded operator<<(). here's a simple example converting bool's to custom strings.

edit : You know what? Never code when it's past midnight and you have bags under your eyes!

Re-Post : manipulator code.

Code:

#include <iostream>
#include <string>
using namespace std;

class myManip
{
    friend ostream& operator<< (ostream&, myManip&);
    string out;

public:
    myManip(bool b)
    { 
        out=( b?"Yeah" : "Nah!" ); 
    }
};

ostream& operator<< (ostream& os, myManip& mm)
{   return os<< mm.out;    }

int main()
{
    cout << myManip(true);
    cin.get();
}

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