what is : operator ?

This is a discussion on what is : operator ? within the C++ Programming forums, part of the General Programming Boards category; what is : operator ? what it does ? i know about scope resolution operator. it is written as :: ...

  1. #1
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    what is : operator ?

    what is : operator ? what it does ? i know about scope resolution operator. it is written as :: but what is : operator ?
    can anybody explain plz. i dont know the name of this operator.

    if anybody give very simple example, will be glad.

    probabily these are written inside a class.

    thanks
    blue_gene

  2. #2
    Registered User jlou's Avatar
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    There is no such thing as operator :

    However, there is the ternary operator, which uses ? and :

    Code:
    #include <iostream>
    
    int main()
    {
        bool expression = true;
        char result = expression ? 't' : 'f';
        std::cout << result << std::endl;
    
        expression = false;
        result = expression ? 't' : 'f';
        std::cout << result << std::endl;
    
        int var = 10;
        result = var == 10 ? 't' : 'f';
        std::cout << result << std::endl;
    
        var = 20;
        result = var == 10 ? 't' : 'f';
        std::cout << result << std::endl;
    }
    If the expression evaluates to true, then the first value is returned, otherwise the second value is returned. I think you can overload the ternary operator for a class, but I think it is rarely a good idea.

  3. #3
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    ? : is the tertiary operator.


    a < b ? a : b;

    the above line is the equivalent of

    if(a < b)
    return a;
    else
    return b;

    In more general terms it says if the conditional statement before the ? operator is true then return the variable before the : operator, else return the variable after the : operator.

    : is also used as in initialization lists for classes, and maybe more. ? may be used for other purposes as well. But when used together, that's what it does.

  4. #4
    Code Goddess Prelude's Avatar
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    >I think you can overload the ternary operator for a class
    No, the ternary conditional operator is one of the operators that cannot be overloaded.
    My best code is written with the delete key.

  5. #5
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    i am well aware of the ternary operator in C . i have seen these to use for the class constructor.i am sorry, i dont have the example right now . but is there any other way to use this operator in a class ? or any other application except this ?
    blue_gene

  6. #6
    Code Goddess Prelude's Avatar
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    >i have seen these to use for the class constructor.
    You mean something like this?
    Code:
    myClass::myClass ( int a, int b, int c )
      : mya ( a )
      , myb ( b )
      , myc ( c )
    {}
    The colon simply says that what follows will be an initialization list followed by the constructor body instead of just the constructor body. The ? operator is only used in conjunction with : as the conditional operator, but : is used elsewhere (bit fields, inheritance, labels).
    My best code is written with the delete key.

  7. #7
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    exactly i was talking about that.

    The colon simply says that what follows will be an initialization list followed by the constructor
    not clear.

    what is the equivalent code of that ?
    your brackets are not properly written probabily
    blue_gene

  8. #8
    Code Goddess Prelude's Avatar
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    >what is the equivalent code of that ?
    In this case:
    Code:
    myClass::myClass ( int a, int b, int c )
    {
      mya = a;
      myb = b;
      myc = c;
    }
    >your brackets are not properly written probabily
    ...
    My best code is written with the delete key.

  9. #9
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    yes,latter one i know and that is very simple . i also read about initialization list from my book.

    i wonder, how many ways a simple thing can be made complicated !! there are many syntaxes for the same thing!!

    anyway, its fine....ok

    thanks
    blue_gene

  10. #10
    Code Goddess Prelude's Avatar
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    >how many ways a simple thing can be made complicated !!
    You really don't want to know.

    >there are many syntaxes for the same thing!!
    Well, when it comes to initialization lists, there is a purpose. Create a class with a const or reference member and see how far you get trying to initialize it in the constructor body.
    My best code is written with the delete key.

  11. #11
    Obsessed with C chrismiceli's Avatar
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    You all forgot about when using switches

    Code:
    switch(variable) {
         case something:
              statement;
              break;
    etc.
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  12. #12
    Code Goddess Prelude's Avatar
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    >You all forgot about when using switches
    >>but : is used elsewhere (bit fields, inheritance, labels)
    My best code is written with the delete key.

  13. #13
    Obsessed with C chrismiceli's Avatar
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    You caught me prelude, I forgot about labels and bitfields, haven't done too much with inheritence yet, I still am learning c++. I guess the : operator is the misc. operator. Do all know all operator.
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