Setting default param vals?

This is a discussion on Setting default param vals? within the C++ Programming forums, part of the General Programming Boards category; I'm looking through some code and see Code: void myclass::myfunc(): a(0), b("hello") { //code } I'm having trouble finding anything ...

  1. #1
    Registered User
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    Nov 2008
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    Setting default param vals?

    I'm looking through some code and see
    Code:
    void myclass::myfunc():
    a(0),
    b("hello")
    {
     //code
    }
    I'm having trouble finding anything on google that tells me what this is. What is the purpose of this syntax? Are these optional paramaters that are being given default values?

  2. #2
    C++まいる!Cをこわせ!
    Join Date
    Oct 2007
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    It is called a initializer list. Basically, it initializes member variables with a given value.
    (This is different from assigning since assigning calls the assignment operator and initialization will call a constructor.)
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  3. #3
    Registered User
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    This like a incorrect attempt of using initialization list. The reason it is incorrect is that initialization lists only work with constructors not member functions.
    Code:
    void myclass::myclass(): a(0), b("hello")
    {
    }
    Would be correct if your class had a variable named a and a string variable named b.
    See this link on initialization lists.

    Jim

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