Thread: Creating my own manipulators (formatting flags for streams)

  1. #1
    Registered User
    Join Date
    Mar 2006

    Question Creating my own manipulators (formatting flags for streams)


    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:

    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

    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?

  2. #2
    Registered User
    Join Date
    Feb 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.

    #include <iostream>
    #include <string>
    using namespace std;
    class myManip
        friend ostream& operator<< (ostream&, myManip&);
        string out;
        myManip(bool b)
            out=( b?"Yeah" : "Nah!" ); 
    ostream& operator<< (ostream& os, myManip& mm)
    {   return os<< mm.out;    }
    int main()
        cout << myManip(true);
    Last edited by Bench82; 03-14-2006 at 06:29 PM.

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