Helper functions: design issue

This is a discussion on Helper functions: design issue within the C++ Programming forums, part of the General Programming Boards category; Suppose I have a generally useful function declared in a header that relies on a number of helper functions which ...

  1. #1
    The larch
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    Helper functions: design issue

    Suppose I have a generally useful function declared in a header that relies on a number of helper functions which are not meant to be called by other functions. Where and how would it be recommended to declare the helper functions? Would there be any issues if they are declared in the implementation file (of the useful function) and not in the header?
    I might be wrong.

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  2. #2
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    I would generally declare and define the helper functions in the unnamed namespace of the implementation file, and not mention them at all in the header. I'm not entirely sure if that is best practice, though.
    Last edited by Daved; 02-20-2008 at 03:02 PM.

  3. #3
    and the Hat of Guessing tabstop's Avatar
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    I don't see anything wrong with leaving out the function declarations if you don't expect/don't want the functions to be called from outside the file; I've done it myself. And if it those functions turn out to be "useful" too, then you can add the function declarations to your header file later.

  4. #4
    Kernel hacker
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    Normally, I would use the "Pascal" principle of putting the helper functions above the "external" function, e.g:
    Code:
    #include <somefunction.h>
    
    static int helper1(...)
    {
      ...
    }
    
    static int helper2(...)
    {
    ...
    }
    
    int somefunction(...)
    {
    ...
       x = helper1();
    ...
       y = helper2();
    ...
       return soemthing;
    }
    This is of course both a style issue, and other people may have other ideas of which order you place functions, etc. And if helper1 and helper2 are mutually recursive, then you will of course have to forward declare one to call it from the other.

    By making the functions static, they are not "visible" to other functions.

    --
    Mats
    Last edited by matsp; 02-20-2008 at 02:46 PM. Reason: Adding static to the helper functions.
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