Making C++ operators
Results 1 to 5 of 5

Thread: Making C++ operators

  1. #1
    Senior Member
    Join Date
    Oct 2005
    Posts
    106

    Making C++ operators

    I am thinking about making some operators in C++, but I have no clue how to approach it. Something for "to the power of". Alternatively, I could simply make a void method; but I would prefer an operator.

  2. #2
    Senior Member
    Join Date
    Mar 2004
    Posts
    557
    Hi

    Operator overloading[1] is what you want I think.
    The idea is to redefine an operator in the following
    formal way (here: "to the power of")


    Code:
    double operator^(double a,  double b){
    	return(exp(b*log(a)));
    }

    However, the above example won't work if I recall correctly,
    since operator overloading requires a class/structure for some
    reason. I do not know whether this is true in general, or whether
    it can be bypassed.

    One working, but inconsequent example would be

    Code:
    struct mydouble{
    	double value;
    };
    
    double operator^(mydouble a,  double b){
    	return(exp(b*log(a.value)));
    }

    Cheers

    P.s. Certainly, the above construction for the power of
    is superior to a naive for-loop for two reasons:
    (i) it is more general (double in the exponent is possible),
    thus the square can be taken
    (ii) for an integer "b" larger than 20 or so, it is
    faster. The reason: while the for-loop approach grows linearly
    in "b" the other does not.


    [1] http://msdn.microsoft.com/library/de...tm/overl_9.asp
    If the only tool you have is a hammer, you tend to see every problem as a nail.
    (Abraham Maslow, Psychologist, 1908-70)

  3. #3
    Banned
    Join Date
    Nov 2005
    Posts
    63
    sec_ware has hit the nail on the head, to overload an operator, atleast one argument must be a user defined type as below

    Code:
    #include <iostream>
    #include <cmath> // include for pow()
    using namespace std;
    struct PowerFloat { // define PowerFloat type
           float f;
           float operator^(float b) { // change the meaning of the ^ operator
                 return pow(f,b); // compute the actual pow() and return the value
           } 
    };
    int main() {
           float a = 2.0;
           PowerFloat b; 
           b.f = 5;
           cout << (b^a); // output the value of pow using ^ within () due to operator presedence
           return 0;
    }

  4. #4
    Banned
    Join Date
    Jun 2003
    Posts
    1,302
    Just to jump in and add my two cents... They are both correct, when overloading an operator you have to do it within a class... If I am not mistaken it only works within that class also.

    I wanna say there are some operators that are forbidden also.

    But, I do what all great men do when they don't know.... Turn to a great women and tell her to get my coffee... (Please women don't take offense in that... it was a joke.)

    I use google....

    http://www.cplusplus.com/doc/tutorial/classes2.html

    should give you a nice little read on it

  5. #5
    Ninja Code Monkey
    Join Date
    Nov 2001
    Location
    Washington State
    Posts
    1,027
    Erm, you don't necessarily have to overload an operator in a class. You can make non member operators to do things like the insertion and extraction operators to handle your user defined classes.

    As an example:

    std::istream& operator>>(std::istream& is, <user defined class>& v )
    {
    // code input data for your user defined class
    return is;
    }

    This operator can then be used in the standard way to use "cin >> <your class>;" to get data for your class.

    You might also look into using templates to make the non member operator more generic.
    "When I get a little money I buy books; and if any is left I buy food and clothes." - Erasmus
    "There is no programming language, no matter how structured, that will prevent programmers from writing bad programs." - L. Flon
    "Mischief my ass, you are an unethical moron." - chsh
    Blog of X

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

 Security News

     Patches

       Security Trends

         How-To

           Buying Guides